Hello everyone!
A couple of points:
Gun crews taking cover from enemy fire was a normal practice since the introduction of quick-firing artillery (and even before that). Actually, it was one the main goals of counterbattery fire, since the physical destruction of guns and crews was often not possible. A good reference point is a german breakthrough at Sedan (1940) when french losses in guns and personell were slight and yet their artillery was thoroughly neutralised. This applies to anti-tank gun crews as well. There is nothing "gamey" about that and it has nothing to do with crews "abandoning" their guns. As a matter of fact it's the current system that forces the player to abandon the guns, unless he wants to see his men lying hopelessly in the grass and being ripped apart by enemy shells. Even when the ability to recrew the guns will be introduced, the attacking player has several ways to counter this, all of which are historical and realistic:
1) He can try to disable the guns with direct HE fire, thus making them useless.
2) He can hit the guns with another barrage, if the crew is stubborn (foolish?) and wants to resume firing from the same position (The ability to instantly fire for effect, without spotting rounds, on already registered targets would greatly help here).
3) He can isolate the gun from the crew by direct fire, after the crew took cover.
Consider that when the crew is not manning the gun it's fire is neutralised, so I fail to see any "gamey" effect against the attacker.
As for the the guns mobility:
Smaller AT guns and infantry guns should be moved around the battlefield as they were historically (with proper consideration for terrain, crew fatigue etc.). They were designed specifically to follow closely the infantry and provide support against those targets that couldn't be neutralised by other heavy weapons. Again, nothing "gamey" about that. If someone tries to use them as tanks, he will be quickly punished by skillful opponent.