In closing I would say it is hard to beat a turbo prop climb to altitude
performance, and its weight,  and size to hp merits.  Yes fuel burn is
less than stellar.  The attraction is reliability and for people in a
hurry, in which saving 15 minutes on a three hour flight is a big
desire.  If $$$$ are driving your attraction for having a 1000 hp engine
then I  would venture to say you could buy two  turbo prop engines for
the money it would be required to develop the various rotary systems at
your horsepower desires.

However if you have the burning desire and $$$ to develop an unique
engine that will absolutely smash any BSFC records, count me in as a
technical supporter.  Many of the challenges you will face are similar
to ones  people on this forum have solved in the past ten years.

Doug in Japan

Doug,
Just last weekend I spent a couple of hours talking with a turbo mechanic,
he's building a RV9- very similar to the Vision. He was telling me about a
turbo one man can hold with both hands which can be used in a light
aircraft, didn't mention hp but said one was used in an RV in the States,
but like you said fuel burn is double and the cost would be something like
$100,000 - but he said the cost was coming down.
Personally I think a larger fuel capacity carrying plane would better served
with a turbo prop as I believe cost of development would be comparable to a
turbo prop installation , which only leave fuel burn the only remaining
factor.
One could run 3, 13B motors.
George (down under)