No I think Lutes suggestion is worth considering and I can redesign my proposed map to show this.
I was going to run a mountain range around the edge of the main island north of FT Island about 40000ft height
You could also bury the towns to sea level like having them at the bottom of a very deep well. Of coarse vehicles would have to be destroyed at a 5000ft drop wouldn't be fair other wise
Not sure on number of bases left to reset map but I always thought it was down to the last 1 that a country has.
Could be wrong