Bear in mind I am still new to this system so everything below should have a pinch of salt added just in case.

With that being said, as far as I understand. RAW, an attachment does not require any sort of roll to install, you pay credits to buy it, slap it on your weapon and boom, away you go. My question involves the lightsaber and certain attachments, eg; Curved Hilt, Superior Hilt Customization etc etc. By the RAW you pay credits and no roll needed. However, would you think that as a GM i would be correct in making my PC's do some sort of roll for such attachments being installed, even just a simple difficulty one ? my reasoning being that you are rather drastically changing the whole weapon and not just bolting on something.

Cheers in advance

You're correct in that per RAW, installing an attachment doesn't require any sort of roll. Just buy/acquire the attachment and plug it into the weapon or armor. Because you are in effect just "bolting on" the additional parts to improve/alter the weapon.

And frankly, I'd suggest keeping it that way. One major element to this system that a lot of newer GMs don't get right away is that not everything needs to have a roll, and that every time the players do roll dice, it should generally be important to the story. After all, if the difficulty is simple (i.e. no purple dice), then you need to ask yourself "why am I taking time away from the story to resolve a dice roll?"

Modifying an attachment requires a roll because in a great many cases, those modifications are greatly improve the effectiveness of the weapon, especially when it comes to lightsaber crystals; there's a huge difference between a basic lightsaber with an unmodded Ilum crystal and a basic lightsaber will a fully modded Ilum crystal, where there's not quite as much of a difference between a basic lightsaber with a curved hilt and a basic lightsaber without a curved hilt.

Don't forget that some of those attachments are just... a strap. Or a flashlight. Realistically, any weapons company isn't going to make equipment and/or attachments for that equipment that would be difficult to apply to the weapon. They want all of their customers to be able to upgrade their products without having to be trained technicians.

Regarding your concern that Superior Hilt Customization and Curved Hilt specifically might be an exception...

Well, I'd still say no. Superior Hilt Customization just represents a lot of time tinkering with the weapon, getting it "just so" so that it really feels like an extension of yourself. That sounds more like a bunch of Simple Mechanics checks to me, at worst. The real gate to that is the high cost - more than fair, in my opinion, since you have to get doodads and adjustments to make the hilt perfect.

Curved hilt is a stranger case. To me, it's an absurd attachment, since it seems like you're replacing the whole hilt with a different one entirely. And if my player knows he wants a curved hilt from the get-go, I don't see why he can't just build it that way... But I digress. Accepting that it is, indeed, and attachment, I don't think requiring a mechanics check is the way to go. It's already really costly (for some reason), so I'd consider that the only obstacle to getting it. A high cost AND chance of failure is just upsetting if you fail, and doesn't really add fun. If anything, you can say that the hilt was built/found curved and the attachment is just the "finishing touches" to take it from aesthetic curve to functional curve.

Also, remember that a lot of attachments would be kind of annoying (or even difficult) to put on - yeah, you've got your flashlights and your straps, but you also have entirely different barrels for your guns and such that would require disassembly of at least the bulk of a weapon before the swap could be made and the weapon reassembled. However, like piloting a starship, the real life difficulty would be there and not everyone could probably do it all the time, but it's boring to require rolls for everything so the RPG considers it trivial. You don't have to roll piloting during a dogfight unless you're doing something spectacular/avoiding obstacles on top of it, because rolling piloting every turn just to stay in the air isn't cool. Everyone can pilot under stress, everyone can field strip their weapon. Just how it is.

Regarding your concern that Superior Hilt Customization and Curved Hilt specifically might be an exception...

Well, I'd still say no. Superior Hilt Customization just represents a lot of time tinkering with the weapon, getting it "just so" so that it really feels like an extension of yourself. That sounds more like a bunch of Simple Mechanics checks to me, at worst. The real gate to that is the high cost - more than fair, in my opinion, since you have to get doodads and adjustments to make the hilt perfect.

Curved hilt is a stranger case. To me, it's an absurd attachment, since it seems like you're replacing the whole hilt with a different one entirely. And if my player knows he wants a curved hilt from the get-go, I don't see why he can't just build it that way... But I digress. Accepting that it is, indeed, and attachment, I don't think requiring a mechanics check is the way to go. It's already really costly (for some reason), so I'd consider that the only obstacle to getting it. A high cost AND chance of failure is just upsetting if you fail, and doesn't really add fun. If anything, you can say that the hilt was built/found curved and the attachment is just the "finishing touches" to take it from aesthetic curve to functional curve.

Also, remember that a lot of attachments would be kind of annoying (or even difficult) to put on - yeah, you've got your flashlights and your straps, but you also have entirely different barrels for your guns and such that would require disassembly of at least the bulk of a weapon before the swap could be made and the weapon reassembled. However, like piloting a starship, the real life difficulty would be there and not everyone could probably do it all the time, but it's boring to require rolls for everything so the RPG considers it trivial. You don't have to roll piloting during a dogfight unless you're doing something spectacular/avoiding obstacles on top of it, because rolling piloting every turn just to stay in the air isn't cool. Everyone can pilot under stress, everyone can field strip their weapon. Just how it is.

A curved hilt is only an attachment in that that is how this game handles customizations mechanically. It is not actually something you attach narratively.

Use the RAW as it is written it helps to simplify the game at those moments of downtime.

Every roll costs time, and it is really disturbing if you have to brake the session before the last encounter because you run out of time, since everyone had to roll on attachments, jump over a 1 meter long gap, open a wodden Door and so on.

Only thing I always take with in consideration is that the PC needs some time to place the attachment (espacially for lightsabers) so I won´t let him went into the shop, buy the parts and say it is attachted right away. at least let him go back to his place and let him be handwave tinkering for one to six hours, while other PC can handle theire stuff.

Yep, the rolls come when they want their add-on to actually do something extra. Slapping a scope on a gun shouldn't be hard, assuming you have any experience with guns, and I'd even extend that to Force-assembling your lightsaber; it's when you want the crystal to give the saber even more damage, or change its crit value, and in these cases, there IS a roll, a rather important one that, if done wrong, can destroy the component, or at least cost you the upgrade permanently; not so bad for a part you can "just buy in a store", but craptacular when it's that krayt dragon pearl your GM actually let you acquire, after stalking the Tatooine wastes fro a month, hoping to find one of the rare beasts, and then find one that's actually developed a pearl.

A lot of this game seems to have been made very simple, and after playing d20 versions for a decade, and seeing the WEG version I'm not fond of before that, I for one, can say it seems very nice of them to have made such things easy. There are plenty of other, better ways to screw up.

Regarding your concern that Superior Hilt Customization and Curved Hilt specifically might be an exception...

Well, I'd still say no. Superior Hilt Customization just represents a lot of time tinkering with the weapon, getting it "just so" so that it really feels like an extension of yourself. That sounds more like a bunch of Simple Mechanics checks to me, at worst. The real gate to that is the high cost - more than fair, in my opinion, since you have to get doodads and adjustments to make the hilt perfect.

Curved hilt is a stranger case. To me, it's an absurd attachment, since it seems like you're replacing the whole hilt with a different one entirely. And if my player knows he wants a curved hilt from the get-go, I don't see why he can't just build it that way... But I digress. Accepting that it is, indeed, and attachment, I don't think requiring a mechanics check is the way to go. It's already really costly (for some reason), so I'd consider that the only obstacle to getting it. A high cost AND chance of failure is just upsetting if you fail, and doesn't really add fun. If anything, you can say that the hilt was built/found curved and the attachment is just the "finishing touches" to take it from aesthetic curve to functional curve.

Also, remember that a lot of attachments would be kind of annoying (or even difficult) to put on - yeah, you've got your flashlights and your straps, but you also have entirely different barrels for your guns and such that would require disassembly of at least the bulk of a weapon before the swap could be made and the weapon reassembled. However, like piloting a starship, the real life difficulty would be there and not everyone could probably do it all the time, but it's boring to require rolls for everything so the RPG considers it trivial. You don't have to roll piloting during a dogfight unless you're doing something spectacular/avoiding obstacles on top of it, because rolling piloting every turn just to stay in the air isn't cool. Everyone can pilot under stress, everyone can field strip their weapon. Just how it is.

A curved hilt is only an attachment in that that is how this game handles customizations mechanically. It is not actually something you attach narratively.

Fair, but why can you add it later? Why is it not a think you build the lightsaber with? Theoretically, my PC had the credits at the time to build it with the attachment. It's just odd.