johnwitts: I'm also trying to work out how feasible it would be to use a gas turbine with a CVT instead of a piston engine.

John, Chrysler experimented with a commercial turbine engine for automobiles 38 years ago. Check this out:

http://www.autospeed.com/A_0764/P_1/article.html

The cost was quite high - although probably mainly because of the limited production. In the end, the turbine engine had two problems - it couldn't meet evolving emission control standards and it wasn't capable of getting good fuel mileage. It could burn almost any hydrocarbon, though which may have compensated for that.
The engine was coupled to a normal three speed automatic transmission after a reduction gear train. I drove one briefly and found it quite responsive for a big car with a relatively small (130 HP) engine. The sound was a fairly quiet whine - which didn't appeal to my teenage desire to hear a big throbbing V8 when I stomped the pedal.
My Dad's friend at the Chrysler dealership drove the car for a few months and loved it.
No CVT though. Not sure the turbine engine would fit in a "Fiat Uno".