you should be using your UVs as a guide for where your texture goes. Scale should not be an issue if you have correctly used your UV layout... at least i don't think so.

for a wall i would planar map the wall, then i would unfold the UVs and lay them out. then export that at 2k as a targa or tif. open it up in photoshop and then do all the normal business of creating layers and sorting out the textures according to where my uv guidelines are.
thus scale should not be a problem.