According to the RFC, you can only list up to 5 nicknames, so that doesn't really solve much of the problem. At best it would make a 500 user channel more like a 100 user channel-- which is still way too many commands (join 3 of those channels and you're looking at a command a second just to keep up, which is again, not uncommon).
mirc.net's raw list says that other networks might support more than 5 nicks, but mIRC could never rely on this, and it's unclear if we're talking 50 instead of 5, or just 8 or 10.
