You don't realize that it's either OP Tiger Ace on release level of broken or it's underpower level of Defensive tactics.
If you limit it by currency, you just need to fill 2 OP units/abilities and just fill the rest with crap. See Tiger + Command tank/Puma/Stug-E*
If you try to limit it by rarerity, you should realize that there are not such amount of bad abilities rather than bad combination of them.
*Oh wait, we already have a commander with those 2
Replace the other 3 choices and you have probably a better commander than one of the meta for 1v1.
PD: as a custom game option, it wouldn't be bad. For automatch, isn't worth the effort in trying to balance such system.