Eons ago, I came across a mod on a server that did the same thing this does, only for belts, so you could run them underground for as long as you wanted, with the same reasonable cost as AUP. Might you be up to rebooting the idea?
Yes, as mentioned in another thread I've thought about an implementation before. It is still on my list of mods to make, but its rather far down and would be a separate mod entirely.
