If they cost less fuel (from 75 to 50-55), they could be an option as a stop gap before your call in tanks. You'll able to have some indirect fire and supplementary AT against light/medium vehicles. T4 on 1v1 is already lackluster but on anything above can prove useful.
I'm more of smaller steps radical than several changes at the same time. It's hard to know how a completely new unit will behave in the game so it's easier to mess up with it's price. Right now it's really hard to justify it (even if you go T1-T4) when the performance doesn't correlate to it's price (if we compare to any of the other light/medium vehicles).
it would probably work fine in the poorly designed mess that is t4. i would still rather have it swapped with the t70 though...