I'd personally love to see an avatar that's focus was on healing. Make its Favor be an increased cure potency, make its Wards be cures, make its Rages be endrains. That sort of thing. Would be good in case your WHM disconnects or something.

Another thing I'd like to see is say if Avatar's Favor was activated you'd be able to summon a spirit alongside your avatar. Then the spirit would do its own thing, you'd control your avatar but with the -atk/matk and the perp costs would still make you lose some MP likely.

But that's just a pipe dream.

I'd also like to see Siren again.