Well having tried it now -
1) Isles map - It's possible (very difficult) to reset.
2) Lake Uterus - Will NEVER be reset.
Because of the position of the uncaptureable fields it means leaving uncaptureable fields in your rear.
Now that we no longer get weekly resets I guess were going to get Lake Uterus from now on, as both LW arenas now have it up.
Unless of course someone can come up with a way or resetting Lake Uterus, but I'm not holding my breath.
I've looked at the map, ran various ideas on it, and IMO it can't be done.
Sometimes wonder if some of these 'improvements' were fully though through.
[edit] It may be possible if you have 3-4 times the numbers of players of the other 2 countries.
Ooops no its not your then Spads v 262s and slingshots v Tigers

Oh ENY - Can you at least make a planes ENY value MEAN something? (No problem with ENY limiting)
At the moment they are all over the place. You have 1942 planes (Hurri IIc for e.g.) being limited before 1945 planes (i.e. 190D9).