Texture optimizing, possible?

Hi!
I am building a game level with Cambodia temple style, and now I am at planing stage about
saving texture space so much as possible.
For example the stone wall at the temple, I am planing to use same diffuse seamless texture
to make a (seamless model) and (no seamless model - with nudged edges).

But problem comes, when I do an AO baking and NM baking.
I have create a separately AO and NM textures that have a nudged edge and not nudged edge.
And then combined these in Hypershade, then assign shader on the mesh depend what kind of stone block I do have.
But then I got stretch problem on these with nudged edges to when I create a longer stone block.

I can't do a extra UV map for these stone block. (Unity3D limit)

So I wonder if some one have done a similar thing and how did you solve this problem.
For further explanation look at my ugly sketched picture.

You may wonder why I want to do this:
- I can create more variation on same seamless diffuse texture map, without creating a separately texture map for no seamless and seamless texture.
- Some times I want to create variation on the stone block size AND have a "end" on the seamless texture. (so it looks like a separate stone block but with nudged edges.)