Greg, I think you hit on the challenges we face with this issue.
I've seen the little under-sink water heaters, and have not been happy with them at all; the best they seem to do is make the water slightly warm. Half a dozen installs, and I've yet to find one that I like. (These were maybe 3 gallon tanks, and not true 'point of use' heaters).
Nor am I all that happy with 'instant hot water' piping arrangements; that's a lot of pipe to keep warm. IF I went that route, I might try to put the circulating pump(s) on timers, for high-demand periods.
Solar and attic heat collectors have merit, but there is always that issue of winter freezing. Before you know it, you have some pretty elaborate controls - and they're of little help for that 6AM shower.
What HAS worked is having a small (maybe 20 gallon) water heater mounted in the attic, above the bathroom. You feed this from the hot water line; its' job is to provide you the first few gallons of hot water while the line warms up. With this arrangement, there is very little 'stale' water to drain before you are getting hot water.
