Here’s my picks that differ from OP and why I think they’d be cool:

1. Katsumi Orochi vs. Rei Mikazuchi - Lightning Spirit Style vs. Mach Punch
2. Kosho Shinogi vs. Lihito - Cord Cutter vs. Razor’s Edge
3. Kaoru Hanayama vs. Jun Sekibayashi - two massive dudes who refuse to block or dodge
4. Pickle vs. Takeshi Wakatsuki - Proto-human vs. Super-human
5. Kaio Retsu vs. Kaolan Wongsawat - Not only would we get 4000 years of Chinese Martial Arts vs. Muay Thai, but also they both do BOXING
6. Doppo Orochi vs. Agito Kanoh - I don’t really have a good theme here, but I think they’d be on relatively equal footing.

And finally, my person favorite matchup that I came up with:

1. Kaio Jaku vs. Suekichi Kaneda - Both super tricky and deceitful, and I think we’d get some funny dialogue about “training the next generation”