There is no LV that has 400 hp with smoke by default. That is extremly too survivable. If it gets patched as so, you will see no pro player loosing AAHT before medium tank comes out.
So in return it would have to loose smoke ability and don't forget to give other LV such as USF AAHT & Soviet .50 Quad hp increase as well. In overall, I quite don't see a reason for buffing this unit. It's doing it's job pretty well, and survivability is actually better than similar unit - USF AAHT & m5 -
Nah just make it 400hp and keep the smoke it's alright.