One more example courtesy of Mr. Hitech to show players they have all the tools to accomplish many things themselves they waste time on with the wish list and complaint posts. Anyone could have splooged down 10sq miles of 1000ft high land in the terrain editor and left it with the default clutter painted tile. Then laid down 3 airfields 1 for each country, HQ for each country and one M Entry object at field A1. Then ask how to upload to the custom arena HOST which many would respond who already do it. The info is in this post to change the custom arena to match play which will launch drones as AI enemies. Then when they launch their ride, it automatically air spawns in the circuit with all the bloodthirsty drones waiting to HO and ram them.
Pretty relevant to this POST's subject. And while I built all that and tested it, I fixed the problem on my current terrain I posted screen captures of.
The original problem.
Rearranging the surrounding mountains to solve the problem which creates a whole lot of new mountain finishing work to clean up the changes.