looking kick *** sandgamer
without a doubt PR needs more statics for afghanistan, so far looking cool, be sure to check alot of references when creating the houses.
Rhino can answer any questions you have on static creation, though he can be sometimes a bit blunt at times but he means well

looks like you have created some of these in the past so you know whats up, just keep in mind texture sizes and reusing same textures, because this is a potential problem if too many textures are loaded can overload a players memory and cause lag/crashes. Rhino can talk you more on this topic of texture management.
Hans Martin Slayer has made an interesting Afghanistan map with multiple rivers, he may be able to help you with some tips, but his was a 2km map so it may be different for yours.
Dr. Rank has been working on a 4km Sangin Afghanistan map for a long time now, he would be able to answer questions for you on references and overall map design. CodeRedFox is also working on a 4km Afghanistan map.
The map project looks very ambitious, 4km maps are a big thing that alot of us want to see PR move towards. The difference in gameplay between a 2km and 4km map is drastically large - it definitely slows the pace of gameplay and allows for much more realistic use of larger assets as well as realism tactics. Maps with 4km scale I think are the future of PR with combined arms combat, it definitely helps create a better experience and will definitely attract a certain type of realism player, and in terms of design, its what the mod is moving towards. Just telling you all this to keep your motivation up, because 4km is both extremely time intensive as well as buggy and super PC intensive, especially with some of the amount of detail it looks like you want to be achieving with this project.
Keep posting updates, I'm sure some other R-DEV's will comment here about your specific questions!
If you are interested in becoming an R-CON, let us know - however at this time we must wait and see because of some unfortunate incidents in the recent past (I'll let you read about that in this community modding area if you want to look further).
Just letting you know for me personally as well as many other R-DEV, we love to see this kind of dedication, especially towards something we value highly (4km detailed map). Seeing your mapping project progress and succeed definitely gives alot of the dev team motivation to continue the progress on the mod, especially because 4km maps is something we are lacking greatly atm and is such a big undertaking!