I can't bet for any of the suggestions made here because all of them look interesting. Anyway just give a bit of love to this unit because right now, as it has been widely argued, is a unit without any role/impact in the USF army.
A few games (before even patch release) are enough to claim for a nerf in this community.
Let's play a bit more and after that we talk. M5 is a crystal unit and hard to micro. Countering it can not be, in any case, too hard with pak40/faust/shrecks.
I'd like to play the commander, but right now it is an instant lose picking it up. Best imo would be the option to switch between normal production/-mp +fuel. And also a Kv2 buff. Give a bit of love to the commander, it used to be funny...