resently my group got their hands on a yt-2400 and they asked to modify the weapons on the ship now i have not found any rules to do what they want so I want to ask the best way to handle their request

the weapon they want is a Medium Ion Cannon according to the rules that can only go on a size 5 - 10 ship but they stated that they are willing to give up more HP to make this happen or they would install the legal weapon a light Ion Cannon but want to install a mod to increase its range but I cannot find anything that says that starship weapons have HP

is any of these options good and will not break the game or is there a better option?

Starship/Vehicle weapons don't have HP and cannot accept attachments directly. However there are existing attachments for vehicles that will provide the benefits your players seek.

Advanced targeting array

Edge Core Book, pg 269

Upgrades Gunnery checks. May be modded to add the "Sniper Shot" Talent allowing you spend a Maneuver to increase the range of the weapon being fired, with an upgraded difficulty.

Oversized external weapons mount.

Dangerous Covenants, pg 60

Allows a vehicle to accept a weapon intended for a vehicle 1 Sil larger. In exchange it takes up additional HP, and the vehicle takes a penalty to Handling and System Strain.

Oversized external weapons mount.

Dangerous Covenants, pg 60

Allows a vehicle to accept a weapon intended for a vehicle 1 Sil larger. In exchange it takes up additional HP, and the vehicle takes a penalty to Handling and System Strain.

Of course, the problem with oversize external mount is that it is EXTREMELY obvious what the mount is there for.

Myself, I’d be inclined to go for a quad light ion cannon mount with Linked 3. You could even put that in a retractable turret, so that it might go completely unnoticed unless someone did a detailed scan and got lucky. Each ion blast won’t be as big as the larger model ion cannon, but you compensate by having more of them.