DB-3 (aka IL-4) and the SB-2 would be good additions to the Soviet planeset. They were replaced later with lend-lease and other more advanced Soviet designs, but up to 1942-43 they were pretty important.
Pe-2 would be a great addition but its bombing was more akin to the Ju87 and 110s of the LW, it was a jabo plane more than level bombing. An important one, though. It didn't have the forward firepower of the 110, but still carried bombs.
We'd need a couple of variants, though. Early models only had MGs, later they added 20mms firing forward. Later models got more and more powerful engines, etc.
We would need an early model and a late model.