-1 Its been discussed before, using zones simply wouldn't change anything, people would sit inside the circle and cap off hundreds of tanks for no gain, same as widening the ENY value - people will still fly a P51D all day without carrying if they gained perks.
Only good Idea i've seen so far is make use to the 8 spawn locations a base has, to enable multiple spawns into a base, campers can't cover multi spawns, if they do they do so with far less numbers, enabling a hole that can be broken into.
This is the only idea I thought that would actually work, multiple spawns require defenders to stay closer to the field/towns rather then camp spawns, because if they die then they cannot protect the field, where closer to town enables defenders to concentrate on the defense rather then camping.