Well I believe people could just join an empty server/something and do games like that. I'm just thinking Halo PC right now is all.
Team Switching too, haha. Would be bad I guess.
I am curious as to why people do not want a join game in progress ability. Could it be optional perhaps?
Halo PC has such a thang and it is very nice (dedicated servers too).
I always liked having some destructible environments, like fusion coils and that Covenant Tower on Halo2 Relic.
I think more things can be made destructible for enhanced fun. Maybe certain maps can be while others aren't.
Library on Legendary was indeed hard. But if you practiced enough you could skip some big battles and thus harvest the good weapons for when they were needed (rocket launcher for the elevator rush, etc).
Fun level.