SU-100I (USSR, Tier-5, TD, premium)
Historical Reference:
The Soviet Central Artillery Design Bureau was working in several areas simultaneously, one of which was an initiative of A. S. Chasovnikov to reequip foreign vehicles. A number of reequipment options were proposed for the American M4A2, including repurposing it as an SPG. The project was considered in February 1944 but was not adopted, primarily because there was no requirement for modernization.