try to make the border textures to follow the roof line

Considering done! (Thanks to Daniel118 who is the expert)

Or even better a selectable texture for each border

I think is not better (not now).
Imagine a roof with 87 faces, each face with an average of four sides (borders).
After you calculate this let me know how long could be the list.

On the other hand, I feel you as a programmer: why not take the source, modify and try your wishes than share it with us?

PS I'm SORRY if I managed to upset you [:((]