The only idea I can throw in is to make an under used ability more used, change scavenge to give 10% of the units fuel cost in return and change thorough scavenge to give 20% so scavenging a centaur will give 10 fuel and a IS-2 will give 23 or 20/46 with thorough scavenge. I think scavenge was one of the things to offset the fuel income but I don't see it doing enough since the most I have used it in a match was 3 time so 15 fuel.
Other wise I like a lot of things I see in the thread but I would like for them to be more unique, people want volks to be like rIfles being your early and endgame infantry despite having obers being available even if they aren't enough right now. I think they can work with a reduced income, 5 vet, and trucks they just need to be adjusted to certain levels, perks can be introduced and mechanics can be tweaked. Carlos's ideas do look like a good start.
I think this is one of the keys here. The okw reduced income is supposed to be offset by scavenge, but it isn't really. Especially against USF where people don't really build weapons teams anymore, there isn't a lot to scavenge. I think making scavenge % based is interesting. One issue is that it can really snowball if you lose an expensive tank because that just rewards them with even more fuel.
Looking at scavenge and how to give it more utility would go a long way to make okw more fun to play. While the reduced income isn't necessarily broken, you do feel like you can't really afford to get many vehicles.
Also, I do like carlos danger's teching idea, I think it's really interesting. Obviously would need to be tweaked to get the balance right, but the general principle is really interesting.