Quote: "Still...might be good to have an individual modular set for users that have a single texture that could be painted over with paths or whatever to suit their needs"
If the edges of a 10 x 10 were designed like a seamless texture so that the opposite edges match then the other 8x8 inside part of the section could contain variations.
If each sections edges matched where the prefabs could be rotated, then the possibilities for terrain variation would be even greater.
Yet, all with the ease of placing 16 (or less) prefabs.
The terrain itself could have gullies for sectional matches for rivers, etc.
While those sections would require placement next to a like section, it could still offer straight or turn variations for placement.
Think about it as the river sections all meet in the middle of the edge but run differently through the middle. (varied widths and depths except at edges)
The water itself could be external of the terrain and done with trigger zones and decals I guess, but anyway...
...it was just a thought.
Don't let a crazy idea get you side tracked on this great work though.

I love what you have going on here.