Dont over equalize tanks.. you can balance them via spawn timers, increasing Abrams ticket costs, (edited: fixing frag rounds to not do zero damage to light vics), buffing laser guided ATGMs to be less RNG (they do more dmg) etc.
T-72 does have a smaller silhouette and frag rounds, it is not completely inferior.
Im guessing you didnt want entire teams to suffer because of inferior tanks, but this is BF level of lazy balancing im sorry.
Besides, if reverse speed is such an issue you can add T-80, it has 8-11 km/h up from 4km/h :)