USF
1. WC-51: allowing the Jeep to function as a Kubel that can carry infantry is very interesting. However, now that it can function as an early-game capping unit, I see little reason for it to scale so well into late game. I would remove the artillery ability from the WC-51. Alternatively you could make the Kubel scale better into late game.
TL;DR: either nerf Jeep late game or buff Kubel.
2. Cavalry Riflemen: I don't see it being especially useful. They perform well at close range, have an effective supporting ability, and work well when stuffed into a Jeep or an M3 Halftrack, but would you pick Mechanized for this unit? Personally, I would opt for 5-man Assault Engineers over Cavalry Riflemen in almost every situation.
3. Elite Vehicle Crew: much more attractive, but it is additional micro tax. Don't know what can be done to remedy this.
4. M10: I still don't quite understand the HE shell's purpose. Seems to me it is part anti-infantry, part vehicle crit, but I don't know when I would use it, except maybe used to displace lone MGs defending a VP.
Replacing AE with cavalry riflemen would actually make the commander a lto worst cuz cavalry riflemen are panic unit if you lose a vet 1 riflemen snare squat and need to repalce that unit plus smoke and the thompson with a bar