VCOH's MP system wasn't harsher and it isn't even comparable, as the MP income was dependant on territory held and not a constant rate. That ment that you had more MP income going toward mid, and the difference between base and mid is exactly what allowed you to field tanks while still paying the maintainance costs of your infantry. In CoH2 you simply can't do that. Hence the game degenerates over time. To reflect the all new constant resources system of CoH2, Tanks must cost significantly less MP, simple as that, which would allow you to maintain both your infantry aswell as buy new tanks and with that effectively ending the spamfest and giving infantry a strong presence on the field, instead of being useless cannonfodder as it is now. Upping fuel costs would push tank timings further out, increasing their rarity (which is a good thing in the context of CoH) and putting more weight on both the non-armor defense/offense play, and capturing and holding points for extended periods of time, so this would be a nice addition, but that isn't actually the main point.
Edit: The other half of the issue is that MP decrease/pop was significantly better mapped to the actual costs of the units you could purchase.
1. VCOH's MP system tended to be harsher. At most, you were only going to get +12MP from the map. Still significant but didn't really offset it. Also, your base MP rate was never +300 in VCOH unless if you had supply yard lvl 2 and you had good map control
2. Tanks costing less MP would mean more MP for fuel caches, thereby offsetting the fuel increase anyway. If you want tanks costing less MP so that infantry gain a strong presence, that's a bit too newb friendly I'll have to admit. Although the potency of AT weapons do need to be improved, that's really not we're talking about here.
3. There was one patch where T-34s used to cost 240 MP and idk how much fuel. That is the cost of a conscript squad. The result was simply spamming T-34s, esp if you had a fuel cache. Especially when you hit endgame, as MP becomes more precious, reduced MP would only result in more tank spam.
The armour/infantry relationship needs to be tweaked, I'd agree with you, but this is not how to tweak it.