That actually wouldnt be a bad idea for another scheduled one...*pss* GM's...*hint*, and yea most of the time low levels characters can join too.(they sometimes make you use a novice, like say your name is Tor on 11/15/06, your novice will be Tor111506 or something >_>. just letting you know , welcome to hero too.
Well, the thing about planned event is that you have to make sure you can be there if you're the GM.
I do planned event sometimes, but not always because I'm not sure if I can be there 100% and people get mad if something is announced and then cancelled. But I'll consider doing more planned event in the future, specially for Light & Dark events.
As for levels, most events are open to everyone, some are made with event novices, other with your real characters. Sometimes I'll add level restriction, specially if the event involves pvp.