I'll get ahead of myself and go ahead with my Mt. Moon species votes then.
Well expanding on my dual-personalitied Paras idea, we could have a peaceful, kind-hearted paras infected with a destructive fungus. Could even have a dex entry that ponders about why they are so happy when death is iminent. Enta if it's a girl, Thale if it is a guy (the names are based on the name of one of the classification names of the bug killing fungus).
On the other hand, for the much more likely Zubat, I suggest one of the non-mimicing/4D-viewing children of Batric and Twitchy. Maybe a fourth wall breaker. Yeah, his father saw the fourth dimension, he can see the fourth wall.
As for Clefairy, if you repel for a Clefairy, there is something wrong with you, and might have to not advertise your Nuzlocke in my sig.
Are you planning on getting the Magikarp?
Finally, good luck with Brock, not that you'll need it with your current team.