Use a Puma on the OKW player, and basically work on flanking and hunting down the SU76's before theres too many of them. If you get past this stage and theres like 3-4 of them you'll prob need to use a panther.
The Ostheer player needs to keep his paks spread out and use a halftrack to keep them crewed. Wont kill the SU76''s but at least you'll hold the ground until you can get something bigger.
Stugs can also be effective if used properly vs them (dont engage multiple SU76's with 1 stug tho).
Another tactic could be to have 3 Raketenwerfers stealthed, do a false fall-back so he moves them into range.
Regal mines 1 shot SU76's too... something else to keep in mind.
