Graviman,
If my memory serves, the Rakhlin V12 was a derivative of the Audi V12 TDI engine. The engine was re-engineered to lighten it, replace the chain cam drive and accessory drives with gears, replace the turbos, etc, and TEOS may have been involved with that effort. I did a quick check and Rakhlin is proposing a price of $170K for this engine, which is about 75% of the $225K price of a new 250-C20 turboshaft of similar power.
I also liked your comment about putting a high-pressure recip combustion stage between the turboshaft compressor and turbine stages.
Garrett did quite of bit of work on this type of engine back in the 80's.
Pratt & Whitney has also been working on a similar approach using a Wankel rotary combustion stage.