its a multirole tank bro. what do u think should be done? leave its AP rounds garbage? or make it penetrate heavy armor at a fair rate?
If it was just me, i'd rather remove the AP rounds, add a high chance of stun crews on hit for HE shells, also a probability to de-track the tank or easily damage/destroy the engine on rear hit.
It will keep its multirole, but on a different way, and would be far more interesting ( in my opinion of course ) than the current ISU.
Also', its current AP rounds aren't really "garbage". To be honest, I rarely call-in ISU, but the few times I did ( or when i see it ), I did not have to complain about it on this side.