Good points.
I think there is some desire to find an alternative to the tail rotor but the thinking is usually for preventing tail strikes to passengers and other objects. The alternatives are less efficient but have a reason for use.
If Dave is concerned with power efficiency (and he should be with piston engine) then he could improve the efficiency by a much greater amount with low disc loading.
Back in the 1980's the state of Alaska put out a RFP (request for proposals) for a
"Tailrotorless" helicopter. Preventing strikes was the reason stated in the RFP.
No bids were received from any major helicopter company. Only two proposals came in, one was from me. The state decided to abandon the scheme after a news reporter determined that the real purpose of the RFP was to transfer state funds to some friend of a legislator.