Actually, there is already a variable called $tempstyle that is set in ubbt.inc.php. As default this is set to "default" and is used by all scripts. So it is possible to have several sets of templates and change between them by setting this variable.
So the only thing that has to be added is a field in the user table to set which template set to use.
So the real problem is really to do a template set that is easy and understandable.
