I know this is already a feature in the game that you can expand a protection sign past 31x31. But how about making custom protection areas.
To do this you would go into (Ownership sign), and you would see a button called (custom). Click that and you will be brought into a mode where you can tap the areas you want to be protected, and then once you are ready you press done.
Then you would have for example a circle with its center cut out rather then a cube with no center cut out.
Take this as an example of what I mean.
And to make it less tedious you should be able to duplicate that blueprint and paste it into another protection sign.
(Picture taken at 45k)