Orgha
Apprentice
Don't know if it's been said but say you limit guilds to 20.
Whats to stop a guild like eqms making alt guilds like eqms 2, eqms 3....
Limiting guild numbers would do very little imo.
There are several ways of handling this. The one i mentioned in the op was to not allow two or more unallianced guilds from attacking the same target. It could even be made where unallianced guilds can't perform helpful skills or spells on each Other effectively rendering any branches of a formally massive clan useless to combat. I suppose they could refuse to attack each but that's really not the point.
The point isn't to force everyone to PvP with their former friends. The point is to force people to identify their true friends and back them. Sure some social butterflies here have more than 25 friends. But I bet most people commonly hang with under that number. The number can be adjusted. Whatever makes most sense. 25 is just a suggestion.
Another option is to have larger guilds pay a king's tax in excess of the limit..
Say up to 25 is tax free
25 to 50 guild is required to pay a tax of 10k per member over 25 but under 50.
50 to 100 50k per member over 50 but under 100.
Hard limit could be set or just an upper end tax bracket.
Don't take the numbers literally. Just picked to show an example.
This acts as a gold sink for larger guilds. The tax could be one time (suggest higher more like 100k+) or periodic. If periodic and the guild fails to pay the youngest members are removed until the tax is paid.