Ooh lmao.
With doubles in mind yeah, I could somewhat see that working, but in singles it would be a painfully slow and risky set-up: Turn 1 - Switch Tapu-Fini in; Turn 2 - Switch Tapu-Fini Out and Mimikyu in (and hope disguise doesn't get bopped, which it most likely will); Turn 3 - Swords Dance; Turn 4 - Profit. Keep in mind that you gotta do this in 5/8 turns max or otherwise you won't benefit from Misty Terrain's effect, which is the whole point of it.
Besides, they don't really synergize all that well together. Offensively Mimikyu does nothing for Tapu-Fini and defensively they do not patch up each other's weaknesses at all: Tapu Fini is weak to Poison which Mimikyu takes neutral damage from, but is still weak to Steel; Mimikyu is weak to Steel which Tapu-Fini takes neutral damage from, but is still weak to poison. See? You break this core with a simple 50/50 guess and even if you guess it wrong, you still hit them for neutral damage so it's win-win for your opponent either way.