i got different suggestion, try driving from Nagoya at the morning
you will arrive in gero about 2 hours, try gero 噴泉池, free and beside river
after that you can proceed to takayama
You may choose to stay in takayama or Hirayu onsen or Okuhida onsen staying one night
the next day you can proceed to shirakawa-go, suggest to stay one night there
at night you can drive up to the mountain, for the peaceful village night view and also the milky way, it is so damn beautiful especially at winter time.
you may proceed to kanazawa or go back to nagoya
if you like natural, suggest you plan more day around takayama area.
around end of April, Kamikochi will be open up for forest hiking and lodging, and will be close at mid of November
PS: i would recommend must stay at 槍見館, i had one of the best kaiseki in Japan
especially the beef, 10x better than overate kobe beef
Good suggestion! For the previous trip, I didn't plan for Gero, Okuhida and Hirayu onsen due to time constraint as I have allocated more days at Kyoto + Osaka. Next round will focus more on the GIFU and some rural areas of Japan like Kiso Valley. But then, your suggestion is self driving but we have no guts to drive in winter.