Making a 20 USD lightsabre isn't really an UCS sets, is it?
Ultimate Collector's Millenium Falcon - the name implies big and awesome.
Not small and pesky.
When TLG introduced the UCS Naboo Fighter a lot of fans got mad. It was too small and had nothing to do with the idea of UCS. Smaller sets are..well, just smaller sets.
UCS needs that shining light and angelic chorus feeling in order to be special. There's nothing ultimate in buying a smaller UCS set for 20 USD. You have to be serious to buy the sets.
So no, I don't see any small UCS sets - EVER.