Why you aren't able to have multiple gunners in Buffs at the moment:
The current firing system allows one player to gun multiple stations at the same time. If you put two players in there, you'll have the problem of two people commanding the same gun. For example: put one guy in the nose of a B17, the other in the tail. One 109 comes in from high 12, the other from the high 6. Both gunners fire with all the guns they can. Who gets the top turret?
The only way you could go to a WB-style gunning system is by allowing gunners to run only one post, or by "hard-wiring" gun assignments. (think: .join player n, where n is a number from 0 to 127. Each bit corresponds to a gunner position. Default is 127)