A non perk series could include the current Panzer 4, the 75mm or 76 mm Sherman (open to debate, perhaps a light perk for the 76mm, perhaps not), and the T-34/76 with some adjustment for the lack of extra turrent crew or lacking an AA MG (to keep the playing field somewhat even). Beyond that -- Pershing, Panther, T-34/85, JS-2, Tiger I-II, etc. -- it's just a matter of assigning the proper number of perk points.
Charon