I've noticed that not every creeper gets scared by the ocelot fossil when using creeper overhaul for example.
It would be nice if there was a way to add your own mob IDs to either a config list or a datapack.
This is would be very helpful as pack maker.

This behaviour gets added by a mixin to the goals of a Creeper. It seems like Creeper Overhaul's Creepers do not extend the Creeper class.
Adding this to more mobs using a config seems not that easy because a mixin is really specific.

To anyone reading this: if you have a good method or idea on how to add a FleeGoal to a Mob in runtime, please let me know.

I agree tho @YvngMage, that would be really helpful, I'll se what I can do.