fleccy - do you have a timescale for the next version? The key feature for me is the ability to /kick people as without this we cannot really moderate properly.
My suggestion would be to store a 'kicked <date>' in the perms database field in the user table (where <date> represents the date they were kicked). You could test this variable when entering chat (as you do when someone is an admin) and stop someone entering chat if <date> = todays date. (If <date> was not equal to todays date then you would reset this field.) This would stop someone who had been kicked from reentering till the start of the next calendar day.
Another nice feature would be an 'invisible mode' (for admins only) so they could watch the chat without being shown as being in it. I've seen this on a few PHPmyChat boards previously.
Sorry to be a pest - it's a great hack so far