I found a tree with amazing neagari, but I'm afraid that the exposed root system is far too expansive to get into a small enough pot. Any thoughts?

It is in a pot, isn't it?

I would be more concerne dthat the trunk is quite thin, and I wonder whether you will be able to make this look like a tree, instead o a shrub in the end.

For now, I would worry about recovering an dgetting growth. Leave them alone. Stop repotting and moving them about and wait..