I've been getting into the GV's more and more lately, and there's a hell of big hole in the set.
For EW GV's, there's a few good choices.
M3 Stuart
Same gun as the M8, but up to 51mm of armor be the 12(?)mm of the M8.
Crusader Mk II and III. 50 mm of armor, and a 40mm and 57mm respectively.
Would also give us a good opportunity to add the Crusader AA vehicle with twin 20mm's.
BT-7 fast, lightly armored tank. 45mph, but only 20mm of armor on the hull and 15 on the turret. 45mm L/46.
Panzer III F, J, and M.
30mm all around armor for the F, mounting both the 37mm and 50mm L/42.
The J being upgraded with 50mm on the front and rear hull, and turret front, and carrying either the 50mm L/42 or the L/60.
And the M having 20mm applique armor on the front hull and turret, the 50mm L/60, and having the same hull as the Stug III G.