One of my players plays a Frankenstein-esque droid cobbled together from a 2-1B chassis, B1 Battledroid parts, miscellaneous other droid bits, with laminate armor essentially spot welded onto it. The players recently defeated a Magnaguard in an intense game session, and the players are thinking of upgrading their cobbled together droid with parts from the Magnaguard.

Considering the stat bonuses available to organic players when they replace their limbs with certain mechanical ones, would it be fair to give this droid a +1 to its agility if they replace the medical droid legs with those of a Magnaguard?

In my game I would allow this if they paid the same price as the organics would for cybernetics.

I'd concur. If the MagnaGuard has better Agility, and you can acquire it's motive parts, and cobble them into your Gorm the Dissolver Version 2, I'd say it could get the same +1 Agility bonus the cybernetic legs would usually grant. Since they weren't designed for that chassis, its motors, servos, and what have you, and were maybe attached by a chop shop, even if the MagnaGuard was considerably more agile, I'd limit it to +1, same as the cybernetics, unless you also switch out the arms

How do you get them to "pay"? They "confiscated" (read: murder-hoboed) the parts. I'd say they need to effectively pay for the installation, though that could also be silly, if the players, or that player, were themselves competent, and agreed to do some pro bono work, but that's about it.

If you are upgrading (choosing one of the +1 to characteristics), I'd charge as if they were cybernetics (counting towards cybernetic cap).

For myself, if a droid is replacing a damaged limb or "organ," the equivalent to a prosthetic replacement, I would not actually count against the cybernetic cap.

What blackbird said. If they are looking for a mechanics boost, then they should pay the credit cost. If they are looking to just replace one limb for another at no penalty/boon, then they just do it with a decent check.

The creds can be justified in any number of ways. It could be for hardware and software upgrades to interface with the new hardware in order to get the most potential (IE: the stat boost) out of it.

Because MagnaGuard software is easily downloadable...and I'm done whining about that. For the most part, I can see where you are coming from. A MagnaGuard didn't go down clean and easy, nor do they come apart like Legos, so I suppose you would need to buy the components to salvage what of the chopped off piece is still salvageable, and the work of attaching it. It just seems weird that, if I kill a Stormtrooper unit, and pick between them for the necessary parts to get one good set of lamanite armor, and a blaster rifle, with a few mags, I'm not going to drop some credits among them, for their brothers to come pick up, but these will certainly improve me, but if I do the same to a MagnaGuard, and steal his better hardware, I'm going to have to still pay for the hardware. I get it, as swapping out the legs, the motors, and what all isn't nearly as simple as changing clothes, if I can squeeze into the surviving armor parts, but it's often funny to me, after playing years of games with murder-hobos, replacing, and improving their gear by killing the few worthy competitors, to see some people still try to maintain economy, when a store was never even involved, and the characters aren't nearly as likely to find large amounts of stray credits (the Rebellion wants to look the good guys, so they aren't just hacking the Empire's blood money accounts for funds). Sorry to be snippy. Like I said, I do get it, and I suppose I'd rather the droid have to pay for the stat boosts, the same as the organic players, if they wanted cybernetics.