This is one thing that always really bugged me and that was that basically all the avatars have the same stats bar a couple of extra points in their own respective fields, I think by now the stats should be noticeably different between them all.
I'd love to see titan with huge HP and defense, or ifrit with a large pool of STR and attack, something to really make each avatar truly unique for more then just their blood pacts.
The other thing i would love to see them do is make an avatar ability that doubles their cost and "Upgrades" the avatars to a true battle or defensive "mode" where the receptive bloodpacts are more powerful and the other bloodpacts are no longer selectable in that mode.
For example since titan is my fav >^.^< When you activate battle mode he punches the earth and pulls out a large hammer and his bloodpact rage's do increased damage and you get 1 new one only available in that mode. Or if you activate defence mode he punches the ground and pulls out a shield and looses bloodpact rage and can only use ward and gets 1 new one again only available in that mode.
This kind of thing would truly do smn justice since time and time again we get the cold shoulder with gear that isn't just for us and lack of a decent update for our timers/abilities.