I will admit that i am not the best at making tanks but i just want to give some tips that kind off fix the problems i see with some tanks...

1: Elevation/depression Pretty improtant that your gun moves up and down, these angles are often limited by the gunbreach or sometimes autoloaders.
It is also limited by what is below the gun because it can't go down if there is something in the way. Some tanks have more depression over the sides of the tank.

Anyway with that said i recommend that if you can modify xml files you should limit the minimum input so that it doesn't have 20 degrees of depression because i have not Heard of a tank with that
(i mean you could design a tank where that was possible and then it is normal because some tanks have more than others)

2:
Guns, some tanks fire boom's and then you should edit the firing delay because the boom's make big explosions like if it was fired from a big gun which means large Shells, they take more than 0.25 seconds so you should probably increase the firingdelay.

3:
Steering, First of all some old tanks in the past have had the rotating Wheels steering but not completely because how would that work?

I recommend using gyros instead of making the Wheels steerable because that makes it less realistic, while the gyros are not the best option it is better and if you want more realism than that you can do like this where one side of the roadwheel is for forward driving and the other is for turning.

This is not targeting anyone btw, just some tips.