Just an idea on how to make multi-turret/gunner tanks and ground vehicles work. Obviously this can be done via a setpos/setdir loop with ships, but the problem is, with ground vehicles, their pitch changes according to the terrain, so this doesn't work well with them. So I'm thinking: how about using setvelocity instead?
Lets say, for example, you were to make a MG that can rotate separate from the turret of a tank. Could you model/configure that MG to actually "touch" the ground (invisibly), and thus be able to "roll" with the tank? The idea would then be, you have a constant setdir/setvelocity loop that just "rolls" the turret wherever the tank goes. Thus, when the tank rolls up a slope, the turret also tilts, since the turret is "rolling" as well.
That's the short of it, I guess. I suppose the idea rests on a bunch of "unknowns" for me though, that is, whether or not you could actually model a turret to work in this way. Or has a better way been found to work this problem? Just some thoughs.