I always have Feuersturm equiped for urban maps, and I'd say it makes me win at least 75% (I'm rank 20ish with OKW randoms 3v3s) of matches on maps like Ettelbruk Station. The fact that it doesn't have anything shiny like a heavy tank or that it only works on certain maps doesn't mean it's a bad commander. Feuersturm is one of the most fun and best OKW commanders imo.
I think the up-in-the-air SPHQ split will do a lot for Feuersturm and Scavenge. Faster Flame Hetzer, Jagdpanzer IV support.
If the awful Opel Blitz were replaced with some sort of anti-tank tool to support Battlegroup, it'd be fairly high tier imo.