Wonderful...
JC, Actually one tile is possable with your existing "mtl_terraintex3" system.
But, that only leaves 2 other detail textures available.
The nice thing about "mtl_terraintex3", is that the number of tiling is adjustable.
Might it be easiest the expand "mtl_terraintex3", and make a system called "mtl_terraintex6, or 8"
In any case, thanks for considering my suggestion...
Have an excellent day...