Taking over OP's can be the best fun. I would HATE to lose being able to do this in a challenging way.
For windy the hardest I have found to take over is Dunes and Ronfrue. Since it is a nice middle ground it is worth doing and fun.
If you want it done then just go do it!
With game starting up on friday that gives you three days to grab an outpost from beastmen. Good luck and have fun!