This is a cool idea, except the multiple KT idea.
Could you elaborate on point 4)? What does make it a STUG mean? Literally change it to a stug? change its profile to be stug like?
The suggestion is not to able to field multiple KT but to have to build a new T4 before you can replace the one you lost, the limit to one would remain.
Imo one of issues with Super heavy tanks is that even if one sacrifices his unit to kill them the opponent can same time instantly replace them (especially in large mods).
Allow more time before these unit can be replaced would help allot in balancing them better imo
Currently JP gets allot of armor and HP with a weak gun for it cost. The idea here is to have a cheaper version with less armor, HP and pop, but keep the ranger to 60. It would serve a counter to medium tanks and TD.