The main issue with the M5 quad isnt just the fact that it comes too early (6:30 if you rush it out)...
BUT it has the capability to kill squads that are retreating and is alot cheaper than other HT's at the level it performs at.
Imo it needs a fuel increase to 45/50 if its going to retain its current stats. If not then it needs a dps/suppression nerf. OR a set up time (so it cant run down squads in the first 7 mins).
Keep in mind that it costs 120 Munitions to get that upgrade. Increasing the fuel cost is pushing back the Soviet ability to reinforce on the field. Quite dangerous for those who use Conscripts and Penals (No call in infantry).
Of course, there's also another possibility we can pursue. What if we moved it's suppression buff to Vet 3 rather than have it from the start and increase vet requirements for it too?