The core concept of losing/winning one expansion at a time and fighting for it is interesting, but making it good is more then hard, you need to have some motivation for people to actually contest those areas, so people just wont ecowhore like on ISIS. But balance it that not all mass is in middle, or it will be snowball effect.
Also, can i suggest you to use more grass textures then one? its ugly
You can make mountains nice with brushes+decals (but before you do it you should have your final heightmap done). Same really goes for grass to dirt transitions, it doesn't feel natural at all.
Back to heightmap, do you really want to have so few chokepoints? What about deleting whole middle mountain? or at least making it small?
Reclaim also doesnt feel natural, its just of type of tree thrown everywhere with brush tool... you can be more creative then that!
But its nice to have another mapper here, so if you need any help just PM me, i'l be glad to help.