{P90 and P90 build is very competitive combination. Sometimes (best build, best player) it could be dominating over big gunners.} = In HINKLEY
In every normal TC scenario, there is a very big disadvantage against other builds, even big gunners, because of lack of range. Also because of not only supermutants spawn in every short range city (Redding, BH, part of Den), P90 is not very popular too.
P90 is also quite rare to be equiped as a secondary burst weapon for snipers, so from my point of view i see 3 current purposes for this weapon: Hinkley, leveling (if you have enough ammo), suicide PK burster in guarded cities (if you have someone else who will loot you).
Back to Bozar (rare weapons).
I think that concept of rare items like Gauss pistol, Gatling laser, cookies, ... is good way how to make this game more interesting, because hunt for this stuff, that could very significantly help one side in TC is also very entertaining.
So i like aproach of obtaining those items in the game, but it has to be very limited so those items will be still rare, not usual (or at least ammo fot those items). So even Bozar could be introduced in the game, but my personal conditions:
a) limited resource of weapon (maybe same way like gauss pistols)
b) big det. by every shot (because the same ammo as sniper rifle, we cant reduce using of this weapon in game by ammo)
c) the way how this weapon will introduce the economy circle should start outside the huge gangs (PvP), so i.e. only individuals outside the gang should have biggest possibility how to find that weapon (or weapon part), so the relationship among gangs and "basic" wastelanders would be more important (so maybe PK gangs would have at least one disadvantage against PKs)...