Well, this is a 2D flash game and not a 3D fps game like Crysis...I'm not sure these attachments would work...
Laser Sight seems cool, unsure of how it would improve accuracy since players could just fly all over the place and evade the bullets, but it could work. It's good for singleplayer tho, at least in my opinion.
Increased ammo/Heat coller magazine...oh well...I never wanted reload and such to be implemented into the game (cause I luv spamming bullets m8) but if it is implemented then these two would work perfectly.
Silencer...I don't see the point of that, since a stealth approach is nearly impossible in PB2 (in multiplayer it's impossible) and + it reduces damage...what's the use of that?
Other attachments could be added as well, but overall i don't think they would work in a 2D flash game like this