Add Userthemes to Supporter

Just a thought. It'd be pretty cool to offer Supporters "complete customization". I'm not thinking of giving it to all "regular Joe" supporters, but as part of a multi-level package I definitely see the need for it myself.
I run a standard wordpressmu blog site and allow people to set up accounts for free or as supporters, but it would be nice to add this as an "upgrade" for those with the desire to really customize their theme and willingness to pay for it. Again, just a thought.