Well the new jet has dual FADECs, so you can solve your problem by buying one of them :) I think that for the piston plane market, it's more of a cost/value ratio issue - would you (and customers in general) be willing to pay an extra $50-100k for a FADEC-equipped plane that costs $500k for the whole rest of the plane, just to have the convenience of eliminating manual mixture control? Also some pilots don't want to give up having the ability to control engine temp, power, fuel burn rate, etc manually using the mixture. I know that FADEC-equipped engines have been tested, and will probably be available in the future, it's more of a question of marketing and costs (certification etc) than anything technical.