Well feeding an HVDC line with something that doesn't already naturally generate AC (like a wind turbine) would be a better fit. But it would be a little strange to not fully exploit the other thing that distinguished the DC system from AC: distributed generation vs centralized generation. What was once necessary due to transmission inefficiency is now desirable due to transmission inefficiency :) (among other things). I guess I'll have to wait a little longer for the breadbox sized fusion reactor, though I wouldn't turn up my nose to a residential fission option.