Heavyweights:
Team Surprisingly Deadly Thieves: Eric (DQ11), Therion (8PT), Morgana (P5)
Therion, like other Octopath characters, is a bit worse in this format since using up all his resources to kill one dueler leaves him much worse off for the next one in line. I'm a little hesitant on what to do with P5 Phantom Thieves since their worth swings a lot on whether they get the extra auto-revive or not so playing it safe with a High Middle there (who definitely becomes Heavy given a free extra life). Feel free to replace one of the more obscure characters with FF7 Yuffie if desired for better votability, DK0, since these are all "recentish" in the sense of post-2015 games.
Team ...: Crono (CT), Luminary (DQ11), Freyjadour (Suiko V)
...
Team Fliers: Nina (Breath of Fire 4), Sumia (FE Awakening), Rose (Legend of Dragoon)
Rose is a little interp-splitting on starting Dragoon vs. not, so maybe I'll edit in someone more consistent. Maybe.
Lightweight:
Team Mostly Harmless Thieves: Ashe (FE 3H), Chad (FE6), Male Thief (FFT)
They had best hope Ashe kills everyone, because it's not looking great afterward. Locke is excluded because he says he's not a thief.
Team Servants
Gremio (S1), Brey/Borya (DQ4), Jakob (FE Fates),
Yes, boss.
Team Cats & Frogs Living Together: Cray (Breath of Fire 4), Lethe (FE9), Frog (CT)
Self-explanatory. Cats & Dogs would be dangerous, so better play it safe.
Team Mostly Harmless Dancers:
Primrose (8PT), Dancer (FFT), Azura (FE Fates)
Yep. I considered having a "dangerous" team too but who to stick there after Dancer (FF5) / Jean (Lunar2)? I considered BD Performer here but they're just too horrible even as a joke nom.