Not intending to steal the thread, but wouldn't self propelled artie be an idea?
Not so much "arty" as much as a self propelled cannon. The StG III would be a good example of this. IT could fire the German 75mm HE shell with very similar effects as our current US LVT4 w/ the 75mm cannon. The Priest (or Saxton), and StG III are all good examples of direct fire self propelled cannons.
The indirect fire can get a bit complicated, those who have worked with the Sdkf 251 and its rockets will know what I am talking about.
The thing about the TD that would bring a very different angle to this game is SPEED and firepower. I'm not talking about the 35mph T34/xx, I'm talking of a M18 Hellcat going 50mph+ with a cannon equal to the Pzr. Stop and think how often your tank gets knocked out via one shot. It wouldnt be much different in a M18, cept for its ability to shoot-n-move better. With the way the T34/xx turret is made of cheese... why not take the M18 and be able to evade and menouver that much better?