I don't think I would like to see the slime element anywhere but Tri Ultimate.
Slime, literally, makes null element pointless since you can just hack and slash until your slime turns red and blows the monster up. Even if the monster has high tolerance to slime it'll still go off and do more damage than necessary...
I want the game to keep a challenge, and if we have slime element...that will take away some of the challenge. Don't you think?
Sure, farming is a bitch, but it's just as easy to farm a monster if you have their weakness. So, the only point to slime is just to molest monsters. To me, it's kind of a weapon you mess around with when you just want to screw around.
I love it, but I hate it.
I don't want to see it again at all.