Here is a suggestion that I think would help. How about adding profiles to the queues. You could set up a profile like "residential 256" where download/upload could be 256k using whatever queue type.
then all you would need to do would be to add the client ip to the simple queue and select the profile for that customer.
I know you can do it with hotspot and you can easily set that up with pppoe, but what about adding this sort of thing to the queue tree or simple queues.
Just thinking out lout.
dan
