Maybe the Diesel modified and installed in several airplanes by a company called "Thielert" would have been a good alternate for the Guimbal. (I think it's a modified CDI 190 taken from the Mercedes A Class)
Well, Diamond Aircraft tried just that, and almost went bankrupt due to both quality issues and way overdue shipment of the engines, especially when Thielert went tits up.
As usual, when you want something done properly you have to do it yourself. So they foudned AustroEngine and their DA42NG now comes with AustroEngine's AE300 diesels.
That very engine the AE300 delivers 170 hp, EASA & FAA cert. in 2009, most probably way too late for Bruno to consider as powerplant. Personally I have no idea wheter it is light enough for helicopter applications.