People will just start hosting "almost everyone welcome" or whatever. Enforcement will always be 5 steps behind actors, even when the enforcement is actually paid to do their job.
Likewise, hosting has way too many logistical problems (rehosting, changing rating halfway thru a host being up, changing the type of game, etc) to ever consider something like a time limit on kicking people reasonable. Also, I could just move you to observer, turn off observer, and launch the game getting you automatically kicked anyway.