The answer is not to raise the bar for founding a realm but to make it harder to sustain one with too few nobles. The thing is that's already taken care of. HD just folded and Morek only survived because SA called a crusade.
I would say it does it creates more stagnation and limits opportunities for advancement. A new realm opens up new high ranking positions. Theres no other way to allow as many players to advance at once.
Based on their wiki histories it sounds like most of these colonies had one primary realm backing them:
Everguard (Springdale)
Astrum (Morek)
Shadovar, the precursor to D'hara (Pian en Luries)
Terran (Caerwyn)
Thulsoma (Virovene)
Iashalur (Astrum)
Tol Goldora
The only pre-blight colony effort I can remember that was truly an inter-realm effort was Niselur. Post blight Westguard was specifically crafted for refugees from the sunken continents, it was not a player effort it was a dev made realm.
Even in the case of Tol Goldora three out of the seven founding members were well established in Sol.
Regardless none of these efforts, to my knowledge, were spearheaded by fifteen or more nobles. So the number is still unrealistic whether it's coming from one realm or several.
Tol Goldora had people from other continents lined up to make characters as soon as the realms was founded. There is a difference between how many characters set out, and how many characters/players are committed to a project.
