What kind of combat use have sweeper CEs?
Because you certainly, flame CEs and flame pios aren't struggling and if its so late game that all they do is repairing, then newsflash - CEs are going to be repair and mine only too.
flamer CEs are used lategame cuz of merge, pios are not, sweeper pios dont do dmg, CEs help in fights a bit cuz they dont have to get closer, you pay 25mp for sweeping unit while sovs pay 21/20/18
flame pios are useless after early game when mainline does enough dmg to kill them on approach
in case you lose them 200 vs 170
you pay less for better performance