its possible on a custom map
just reacreate the B17 and remove all the stock guns and replace them with whatever u like
make shure u use common weapons that have mobilephysics or otherwise they wont move with the unit
ive done this with the prince of wales (the big allied battleship) once
i then replaced all the aagun turrets with phalanx aagatlingguns
no plane was able to hit me
if i find back my old code for it ill post it far ya as an example (if u would ever consider to create a custommap)
greetz RED