Real time terrain alphamaps texture swapping

Hey all,

I'm still pretty new to Unity, but I've been working for a while on the same problem now and I was wondering if anyone has an innovative solution.

What I want to do is create a script that will swap the textures on the ground a few at a time, based on a propagation model.

However now matter what approach I take (I've tried Coroutines too) there is a big 500ms hiccup between terrain texture updates. After a reasonably extensive search I've discovered many other people with the same problem (It apparent was not such a big issue in unity 4)

So Unity people, what would you do to accomplish this? If the standard unity terrains are not made for real time deformations and texture mapping, is there a terrain like asset out there that is?

My heightmap is 1024x1024, and my alphamaps are as well. I have 5 ground layers total.

Thanks, L4z0r