Hi,
yes, and ngui also has some amazing features like with one call you can swap the ui atlas and you have something looking completly different.
the one thing I find hard when switching skin is that each skin has different widgets behavior, so you can't really turn a girafe into an elephant without actually having to design your girafe and elephant... so switching skin yes, but that's only a pur graphical switch, the behavior, size and meaning will be exactly the same, any other wish will require two different UI design and behavior, not just a skin swap.
your case is very like this I guess, cause a knight will have different behavior than a wizard, different animation names, different purpose basically. So I would think that you will need a different set all together, not just a graphic switch.
bye,
Jean