As if the Soviet Union didn't have enough premium tank destroyers already, how about another one? The ISU-130 is a likely candidate.
|An ISU-130 boops a Panther on the head during trials. The muzzle brake has been removed to study recoil lengths.|
The ISU-130 had pretty much the same mobility as the ISU-152. For the purposes of making a premium tank, it could lose that fancy modernized engine, and become close to a stock ISU-152 with a BL-9S installed. The larger caliber would obviously increase damage. However, caliber is a double-edged sword, as it would also decrease reload speed. Real life ROF was about 2 RPM (this TD lacked the IS-7's autloading mechanism), so it would have to be boosted just a tad for this to be any fun. Considering that the devastating BL-10 fires at about 4 RPM, 5 RPM for a smaller caliber should be fair.
The ISU-130 was also equipped with a Hertz panoramic sight for indirect fire, but an artillery role is unlikely, considering the relatively small caliber and the TD designation of all of its ISU cousins.