If you want I could join the team
I'm currently working on a lightweight (optimized, not low quality) overhaul of RTW's environments. I will implement it into several mods including RTRVII, RTR8, RSIII, XC5, vanilla rtw, bi, alexander and many more. If you want I can implement them in IB too. Putting my environments into more mods is not a big effort since in the worst case I just have to swap 1 or 2 climates to fit the map area of the mod (to swap the sub arctic climate by a tropical jungle climate for rtw alexander for example). Just copy paste work
Regarding performance, I'll try to make my environments as lightweight as FATW environments, which are only slightly heavier than vanilla.
Here are several screens of my environments: