cold is agony. I have no interest in "adapting", and broaching the idea to my wife is a complete non-starter.

And lukewarm is exactly the same problem; 5 minutes to get that temperature, and some minutes to get it back if you leave the water off.

I am looking for a solution, not for someone to try convincing my entire family that we should prefer the problem. :-P

On-demand water heaters, or electric pre-pumps, or a needle valve with continuous return, are the three viable solutions, period.