Silencer: I am quite against any kind of "style bonus", at least while the insane "2x just cause you used this gun" is still knocking around, but this could be a way to implement it. Thers a negative side to getting your style bonus, though i dont think DA is the kind of game where less muzzle flash matters much
Laser sights: I like the concept, but not sure how fun it would be to have a game of rooftops with 16 dudes running around flashing lasers like its a rave party
Ex mags: This depends on how much ammo aand how much longer reload time.
Scopes: No, i dont think "nuff" was said
What would be the downside to scopes? Additionally, anything with more zoom than a Holo sight just encourages camping imo.
Ex barrel: Is there even dropoff damage in DA? Seems like that might be a way to reduce extreme cases of camping (that 1 fucking roof in rooftops). And if that ends up being the case, less dropoff just makes camping eaiser, which we should be avoiding as much as possible.
Hollow point ammo: Ehh, I would need to see it in action to know for sure, but I am already imagining putting extra damage on the beretta or the mp5 and I am just horrified at the prospect.
Flame rounds: No. Perhaps this is just me, but i HATE it when burn effects get set like this. If this is REALLY asked for then do it like Loadout. Shots do half dmg on impact, and the other half burns over time. Additionally, there needs to be ways to fight it as the player getting burned. Rolling to reduce flame dmg comes to mind, though that might interrupt flow if you get hit in the middle of a big fight
Rubber Bullets: As much as i hate to end on a negative note, a big fat no to this one too. This sounds like a great idea at first, but what happens when 8+ people are all using bouncing bullets? Unless they only bounce once (in which case they would be useless imo) you wouldnt be able to take 2 steps without running in to some dickheads shot.
Overall, good ideas, just try to think of how they could be abused in the future.