I'll start by ignoring the interpersonal drama and comment on the idea.
I'm pretty much 100% against the OP's proposal - It seems to come from the right place, but it's the wrong idea and has the potential to exclude legitimate interests.
Tbh if a minor town is trying to disrupt your inter-alliance battle schedule, all you have to do, as the two established fort battle sides, is get the word out to ignore the prime-time spam battles, focus on the real one, and then take back anything you lose off-prime. If a town can take a fort, they must also defend it, all good. That goes for majors and minors alike.
You've also now got the possibility of mod intervention under certain circumstances, such as the minor player isn't actually contributing to the quality of battles, and if both sides agree it's nothing more than disruptive to their community.
If your world doesn't have battles, and a minor town digs your forts, that's not a problem. You own forts, you have to defend them. No one is intrinsically entitled to own any given fort.
And just to add to that, when these changes were originally discussed, I recall that Syntex wrote that players would have a possibility to vote on the implementation of the rules. However, barely any feedback from the .net community was asked, except for select few which increases the chance of bias or one sided views. While the fort number limits were surveyed on the individual worlds, which I applaud, it would have been nice if you surveyed the implementation of digging restrictions as well.
This was indeed the case when this was simply a local policy implemented to counter Naughty Pumpkin's behaviour on Colorado, of which Colorado obviously agreed to. I seem to remember the same conditions being offered to other worlds, some accepted and some declined.
Now it's a game-wide "rule" because of the situation on other servers - the implementation is still up to the local team and our local team is good with this kind of thing, as evidenced by how they (along with the Colorado fort fighting community) handled Naughty Pumpkin.