I will be in Japan from October to February, and I could try to look for some missing systems (from the miss list in the wiki) there... I can't promise anything though
A lot of the missing ones are probably pretty obscure, but I'd love to see some of these: Bandai Supervision 8000 (1979) and games, more games for Gakken TV Boy Compact Vision (1983), My Vision (Nichibutsu, 1983) and games, Casio PV-1000 (1983) and games, and missing stuff for Epoch Cassette Vision and Super Cassette Vision. That's a quick list, so I could come up with some more details if you have questions.
I agree. For Epoch Cassette Vision as example, I found only one game (Wheelie Racer [d1].scv) in internet, but no dumped bios. Maybe someone can ask Takeda Toshiya, not sure he will help ?