The thing I think of, is shouldn't turrets be another model? As if you look on the models of every tank, the turret is another model as it moves.
cant you just slice it off later? besides it's only another model because it needs to turn around when you want it to turn around.
You could do that with bones, but it would end up really glitchy. Steal the BE APC turret and put an arty cannon on it. Instant win.
I modelled a battleship a couple of years back for this mod but my unwrapping/texturing skills at that point were non-existent so it ended up going to waste. I did pass it on to someone that was going to texture it but never heard back from him. If you want the model you can email me: Dargish (at) gmail.com http://forums.empiresmod.com/attachment.php?attachmentid=50&d=115694329