Do you think I should handle it with many areas of regional textures?
No
If something is classified as the same landcover but looks different in reality, we can use regional texturing to distinguish it only if we're talking about 150+ km sized chunks of scenery which are well separated by some unchanging landclass (making Kauai looking different from Hawaii Big Island works that way because there's ocean inbetween). But we can't do irregularly shaped small-scale structures that way, that needs edits in the landcover.
We can create look A, we can create look B, but not both of them on demand for the same landclass. Are they actually the same landclass on the server, or are they really two different landclasses which are just merged by materials.xml?
Another thing which occurred to me: I designed and tested the scheme essentially on Canaima - which is a fairly small region, and assumed it'd improve the look of things roughly everywhere in the jungle-covered (= bright green on satellite pics) part of South America, and based on that I chose the geographical limits. I am fairly ignorant about how scenery is like across most of South America, so it may be that these limits are too large and there's scenery which looks very bad with them, or that the limits can be expanded to cover a larger area. So feel free to play around with the size of the region - if it can cover more terrain to good effect, that's nice.