Just to get this right:
You want a normalmappingshader with:
2 normalmaps (1 general + 1 tiled for extra detail)
2 diffuse maps (again 1 general + 1 tiled for extra detail)
?

If thats the case, it is very possible indeed.
As for 3dgs's texture channels: I'm currently working on a shader which uses 8 textures. 4 through entSkin and 4 thorugh mtlSkin, so there is no problem on this side.

Shade-C EVO Lite-C Shader Framework