So, i personally see some problems with this:
1. the best way to charm multiple creatures at level 6 would be Hypnotic Pattern, but if you get someone with that spell they are basically out of the fight
the most efficient use of command is to chain opportunity attacks of summons for a lot of reaction damage, so it would immediately break the charm
for a creature to be charmed in the first place, most of the time a wis save, the same as command so there would be not a big difference between charming a creature or just normally use the ability
But now that i am the bad guy saying this i will try to find the best use for this ability.