T70 is insane in team games. lowering cost would just mean more spam!
Team games can't be the base line for 1v1 balance. T-70 suffers from the same circumstances as the T-34. When they pop, Ostheer is starting to ramp up armor production so you need AV and not AI, they are too weak to win vs. any Ostheer armor and they delay the SU-85 considerably. They can also easily be shut down by Panzergrenadiers.
Lowering the fuel cost would put them on field earlier, force an earlier panzershreck on the german side (well, he'll get one either way) and gives it more room (time) to maneuvre, while improving the T3->T4 transition situation (which currently is extremely hard to do with the current meta).