Which is still less fuel than t3+t4 now, by a lot, and a less than 2 su85's. That's what you give up right now by getting the hard counter to P4, you give up getting to ram anything that gets near the 85 (unless you pick one of two doctrines). You are supposed to have to make tradeoffs as Soviet, I am not arguing that you are interested in nerfing Germans.
I agree that fuel requirements would be a major point in balancing an idea like this. That said, I understand the design theory behind the soviets is to make tradeoffs, but I just do not believe it makes for compelling gameplay. The reason the germans are so popular and fun to play is because of their consistency and ability to bring the tactical concept of combined arms to the battlefield at every stage of the game. It's thoroughly satisfying and feels like how the game should be played. With that, soviets and their either/or tech system really fails to capture that element of play.
To me the soviets feel like a poor mix of coh1 PE and Brits. The either/or nature of the PE tech, and the lack of proper combined arms from Brits. It's just a bad place, and while soviets can do quite well in early and mid game, the lack of a full arsenal for combined tactics in the mid to late game is why they seem to come up short, and why they are so heavily reliant on their commander call-ins. These shortcomings could easily be fixed by moving the SU76 and T34 and adjusting tech costs.
Look at it this way, why build a T70 when you can save a little more and get a T34? Why build an SU76 when you can save a little more and get an SU85? The either/or nature not only limits their ability to react to an battle but it also directly lowers the value of units like the T70 and SU76 when their superior equivalent is available in the same building for only a little more fuel. Imagine if the germans had the P4 and Panther in T4; no one would build the P4 if they have they can afford to wait for a Panther, nor would they want to, because by the time you get T4 the match is reaching a stage where the P4 is less effective. This is similar to the stage at which the T70 and SU76 become available, there is only a very small window of time during which these unit can play a role on the battlefield, and you might as well just wait that time for a T34 or SU85.