If I were a betting man with rupees to spare:
SUPER-SAFE BETS:
- Ganondorf, virtually guaranteed
- Ganon, if not accounted for in 'dorf
- Zant, likely playable in dream mode
- Valga -- see above
- Wizro -- see above
- Cia -- see above
SAFE BETS:
- Ghirahim (SS was a big deal)
- Demise (SS was a big deal)
- Groose (SS was a big deal)
- Skull Kid (fan service ahoy!)
- True Midna (fan service ahoy!)
- Tingle (because Tingle)
DECENT BETS:
- Saria (loli fan service, could be "Safe Bet")
- Darunia / Dangoro (Gorons, represent)
- Ruto (fan-wank for Zora titties)
- Mikau (fishbone guitarrrrrr!!)
- Nabooru (Gerudo cheesecake, mmm)
- Ashei (warrior chick from TP)
FUN BETS:
- Twinrova / Koume & Kotake (fire and ice spells!)
- The Yetis, from Twilight Princess
- Adult Malon / Cremia (fan-wank a-go-go)
- Happy Mask Salesman (creepy!)
BIG ?-MARKS:
- Anyone from "Celda," I.E. Tetra, Makar, Medli... How would they de-toon-ify them?
- Vaati... Same reason as above
MAAAYBE:
- Aghanim... Yuga... Shadow Link... Maple... Crazy Tracey...