I was thinking enemies and weapons that we didn't have and i came up with this idea with some help of a friend:
1st) a gun that when charged shoots more shots like kats in T3 (2* = 2 shots 3* = 3 shots...) and kinda similar to alchemers mybe name should be connected with shotgun :D
2nd) a slime that is oposite of lichens -> when killed it splits on more and more in end there are just those mini slimes
"a gun that when charged shoots more shots [...] and kinda similar to alchemers"
Why don't you just use alchemers? At 5* it's a bullet hell and bounces.
Without any more details your idea is lacking something.