In theory then one could reduce the armor thickness and have cheaper(more)and faster tanks.
Yeah, but then things that can’t be shot down by the countermeasures system could get through the armor. Hypervelocity antitank rifles could be viable again.
There is still a role for the main battle tank with its heavy armor. What it does (and has) open up is the survivability of a light airdroppable tank, which the US Airborne is currently starting to pursue. Something with light armor and a big gun that can be paradropped from an aircraft. It can’t stand in the line like an MBT, nor could it spearhead a conventional infantry advance (or be used as a patrol vehicle as in the Sandbox or Syria) but with active defenses it could at least provide point firepower for airborne troops until the heavy armor can get there.