I don't see any reason why using a glow pug wouldn't work to lower the compression needed, as that is exactly what my experience says it does. I don't know if the glow plug works catalytically with diesel fuel. I kind of think it doesn't, at least it doesn't heat up as much as with a battery. How about running a flite pack on the glow plug with a rheostat connected to a thermistor on the head? Heat the plug up more or less as needed to keep the head temp right. I also see no reason why you couldn't put a glow plug in a contra piston.

Actually, you could throttle the engine by changing the glowplug temp.