I think the development just over the last 6 months to a year are more and more indicating that a "territory" limit will not do the job. On COM6 where Phoenix and Nemesis merged (temporarily for the COM6 server) we had no problem fitting all 143 members easily .. and even with smaller boarders that would not be an issue either. The problem, in my opinion, lies in the accessibility (and even optimallity) of massing a server "raid party" of a Game Winning size before launch.
I disagree, limiting the territories helped massively, so much so that a 50 player premade is now very often compared to a meta, just because they have the strength to beat them
Restricting borders to maybe 250-300 fields max (expanded over time with treasuries as it is now) would not stop any Kingdom recruiting as many players as they wished, but it would mean there was less to be gained from it (so less reason for it) managing a smaller team is lot easier & a lot more interesting overall and stops Govs just being tribute mules for their kingdoms