I thought level 10 was maxing for a region. But now I have a region that is level 12 
In the live stream with one of the dev team he said that max regional lvl is 20. But he was not sure about that thou.
My highest lvl was 14 and i had only one rival activ (FNIX tank). After I killed him it droped back to 0 
The thing is that I dont always see the region reset to 0 after killed a rival.
Yes I read a theory in another thread that with each killed rival the score drops by a X points. The amount is probably higher, the higher tier the rival is and the higher its level is. That would mean that my FNIX tank with lvl 4 reduces the score by more points than I had with lvl 14. A prototype runner rival with lvl 1 would reduce maybe only one level.
I suggestend in the last live stream that a kill should not decrease the score but increase. It should decrease if you dont kill machines in an area. We will see if the devs agree with that and implement a system like that.
My first Rival spawned at Level 3 in the marshlands, and I’d killed a tank, three hunters and three runners since the update…
My first was at level three - they’ve been spawning like frogs since, but carrying nothing worth having… 