Some characters I'd like to see in Mugen are:
Yuuki Terumi (BBCP).
An accurate Hazama (BBCP).
Order Sol (GGXXACP).
A good Ryougi Shiki (MBAACC, and no, 41 nor that one that was in 9's site satisfied me).
A finished Powerd Ciel.
Sol Badguy (GGXXACPR).
More good AKOF edits (with 2002UM gameplay if possible or custom like 1%'s Joker).
A 2D Garuda (SFEX).
Seth (UNIEL).
A proper Magus (not a joke character) by Cybaster and Balthazar.
A MOW based Arima Miyako.
And that's it for now. :P