I am surprised we cannot use the self-winding or normal wind-up mechanics for power generation to charge a battery to supplement solar, but I expect the experiments have already been done and it was either not cost effective or just did not give out enough power to be useful.
It's been done and it works quite well from what I've read! I am not sure that Seiko still makes them, but you can still find some new ones for sale. Always wanted to get one of these since they're quite unique.
Unfortunately, Seiko's "Kinetic" movements don't seem to have ever been a big hit, so I don't know if it's something people actually wanted.
Ultimately I think the "problem" is that regular solar watches work so damn well, and that most quartz buyers have no interest in "unique" movements. I mean, I do, but I'm the minority. And I still never bought one...
