I dunno about that, it'd probably still look like a hunk of junk that can barely penetrate most things on the field while tanks are starting to rampage around so the AT boost to T3 would be pretty minimal.
Swapping PM-41 and Penals would be pretty interesting though, there are certainly many times I'd like Penals to have smoke cover for an attack. They're obviously still far worse than Rifles, but if you somehow magically get their flamethrowers in range, they usually do pretty well. And T70 with their scouting ability in T4 would definitely be pure sex.
SU76 actually performs better than T34 against light vehicles, bunkers and more static players with its range and barrage IMO.
I would like to see the SU76 tracking ability removed and replace it with an ability that represents its synergy with infantry (as referenced in the bulletin fluff.) Something like, reload and ROF increase for x amount of seconds if an infantry unit is nearby or something.