1. If you ask me, there's like a bossfight missing from every world in the game:
TT-TWEWY boss
Notre-Frollo
PP-Monstro, Coachman, maybe a thunder-themed clawster?
Grid-CLU
CoM-Full bodied Holey Moley
SoS-Chernabog (that didn't count), Yen Sid?
You could make a whole extra character scenario or 2 out of this many MIA bosses. so....
2. Reverse/Rebirth styled Kairi/Lea story mode
Set after DDD main story but before KH3, Kairi and/or goes into the RoS as part of their new training. The MIA bosses are fought by them in this mode. In my vision, TWTNW is replaced with RG on the night of its fall, as Kairi & Lea both recall what happened that night in their dreams. AX serves as the"rival nort" to Kairi in the way Ansem/Xenmas were to Sora/Riku. Haven't gotten Lea's final boss figured out quite yet.
3. Donkey dream eater
Someone please explain to me how there's a Pinocchio world & no jackasses? How do you screw up something that obvious?
4. Absent Silhouette Xion
Since Days isn't playable in the HD sets, might as well throw her in somewhere else. Perhaps have each of the 4 playable fight a different 1 of her forms?
5. Dream Sword & Soul Eater as bonus weapons for Sora & Riku
6. Drop meter doesn't deplete during bosses
I guess the drop meter can stay for regular gameplay but let's all agree that it had no place in bossfights.