Actually, I think Omega's suggestion sounds like a great idea too, if someone was a member of a newbie council so they got certain "bonus" commands with the character that's a member, why not let them also automatically have those powers and that authority and those responsibilities with any of their characters?
And I agree, Kazro, that you're not going to be able to please everyone with one setup, I'm not sure what you mean by plug ins.. but if the account structure were in place such that it could automatically limit/track things between the characters of a given player, I don't see any reason why the account system couldn't be admin configurable for stuff like that.
For example, on our mud we don't limit multiplay except that you can not multiplay at all if a PK character is involved. So for us we'd have to modify the restriction to only apply if one of the characters in use was PK.
Otherwise, I can really only see positive benefits to an account system. Even the ability to verify the account's initial creation via email so that lost passwords could be sent via email to a known account via automated process or rule updates could be sent to all players already existing and initial email verification could include our rules and so forth. I could even see establishing a subscribable mailing list for news broadcasts via the account system and linking forum membership to the accounts too.
I suppose I'm also envisioning that this account system would have to be mysql based.. I'm not sure if it could be handled through the standard pfiles that are currently used, though I imagine that there'd be a way to do that too, but that it'd make the idea of linking accounts to the forums not so feasible. *shrug*