Idea: Rotating cell boundries.
Here is an idea that may solve a number of issues with perma fields, perma blockers etc.
At the end of each cycle, rotate the cell grid say 5-10km.
This would make game play more interesting with players being forced to deal with different scoring cell areas.
Yes it may mean your forever field is not as effective but I think it would spice things up nicely.
Kudos to LeethalAgent for the idea.