The firefly is a medium tank.
The rest I'll let swtarget pick apart.
Oh, geez, no pressure there.
The M4A3 first:
I want the sherman because it would provide an alternative to the panzer, because we have 2 tanks for the germans, 2 tanks for the russians, and the american tank we have is a perked heavy tank, meaning its not that great for going into tank town and slugging things out. Plus, it was the most widely produced US tank.
Do people even go to tank town anymore? (Oh, wait, I don't think that is what Bronk meant.)
Bronk already pointed out the Firefly is a medium tank, and it is a British rather than American variant at that. But I find it actually quite a capable slugger, so not sure what that has to do with your arguement.
In game terms, the variant designation wouldn't be all that relevant. M4, M4A1, M4A2, M4A3, etc. were all basically the same in terms of armor and sporting the M3 75mm/L40 gun. The variants were due primarily to different manufacturers and different engines, which is irrelevant to a game. (I think the A1 had a cast hull --not sure whether HTC would consider cast vs. welded hulls to be relevant, other than for cosmetics).
M4A4:
For the same reasons as the M4A3(76)W, and because it would give some competition to the firefly, and the T-34/85 because of the thicker armor.
I think you mislabeled your second wish, as the M4A4 is no different than an M4A3 (again, game terms). The "76" versions also appeared on all the A1, A2, A3 etc. chassis, and simply refers to the redesigned turret and a better tank-killing gun (3" M7 on some I believe, 76mm M1 on most, virtually identical in capabilities). "w" refers to "wet stowage" of the ammunition, which again probably doesn't make a difference in game terms (but it sure would make a difference for the real crews).
The Firefly's gun would still be superior, but the 76mm M1 would be very similar to the 85mm Soviet gun. In terms of armor vs. the T-34/76, the Sherman's is thicker in the front hull (by 6mm), but the front of the Soviet turret is a bit thicker, and the Soviet tank also has better side armor on both the hull and turret. Armor is a wash IMO.
Due to the lower speed, the M4Awhatever(76) would probably not get the light perk of the T-34/85 even though the tanks are very comparable in most other respects. Think PanzerIV without the glass mantlet. Oh, and with a more capable .50cal pintle gun for plinking aircraft that are too high to main-gun out of the sky.
And if we can't have these, then atleast give me the M7 priest to play around with.
NO.
Just kidding.