I want a diesel that behaves exactly like an IO-320. Same(ish) weight, size, power, etc. Mixture, pitch, throttle manually controlled, for the same reason I prefer a manual gearbox in the car, and non-turbocharged because I don't want the maintenance headaches. And a semi-affordable replacement for the IO-320 so I can buy an older plane and replace the engine; I'm not going to pay for a whole new plane.
If companies are unwilling to provide such an engine, then my path forward is simple: stick with avgas.