My choices (now that Dancer is almost what we wanted) are Berserker and Mimic.

Berserker would work differently than Monk, in that the natural attacking is automated and rather than chain together abilities, they would have skills that instead affect the upcoming rounds of combat. They could alter they way they fight, rather than simply performing damage abilities. Eventually, they could gain a permanent Haste status and resistances to certain forms of control. For gear they would wear animal hides and fight with clawed gauntlets, and this is different from Monk since it looks better and because I said so.

Mimic is one of my favorite classes in FF and I've been trying to think of how it would work in an MMO setting. Maybe you could gain a few abilities based on the other members of your battle party, or perform the action of the last targeted member, disregarding basic attacks and minor skills/role abilities. Or it might be based on class, so if you targeted a healer and cast Mimic, it would throw out a group heal, or a large single cure to the lowest party member. Targeting a mage would get you a random element spell, and so on. I like the bright, flashy clothing and the masks. Maybe they could use a variety of weapons, or get their own (Bell, Marotte, Scepter, whatever random item might be appropriate).

In case those are lame, I have an idea for a hybrid healer to add another to the game and to make it feel different, like everyone wants. This class would use two-handed hammers and fight alongside the DPS, charging their power with successful attacks. That power could then be expended to heal wounded party members, perhaps building up a personal shield while they fight as well. I see them wearing leather style armor and having some defensive abilities that target members of their party. I think something similar to this would be a great addition since there's really nothing like it in the game currently, and people want something that plays different than regular mage healers.