C-GAME
Yep, the Thielert 1.7 (or is it a 2.0) Centurion, now available in 172s as well. My club looked into retrofitting them to the PA-28-161 but decided against that for now. Given the weight of a PA-28-161 (and the 172 is roughly comparable with the PA28-161) the take-off distance would be unacceptable for anything but the largest GA-friendly runways. So watch those numbers like a hawk!
Mind you, once it's flying it will indeed go to 18.000 feet, and the fuel costs are about 1/4 to 1/5th of comparable AVGAS types.
Oh, and your engineers might benefit from a chat over dinner with engineers with DA-40/42 TDI (or Robin Ecoflyer) experience, so they know what to look for at 700 hours (cracked cylinder heads) and all the other teething problems that this engine seems to have.