I think there is few problems, not with the number of kingdomes, but the reason why we should put tag on. People would want to be on tag alot more if they could have like a personal advantage. Another idea is to create some sorte of realistic role play.
Example: All kingdomes have there own unique armor, wepon, etc. That they can have ONLY when on tag. SO than you could clearly see the difference between people. Depending on the rank you would have different wepon or armor. If there tag become off there armory goes away, but is saved. So when they put there tag back on, they could still have a +12 armor and a persanalize wepon. NO items IN ANY SURCOMSTENCE can be traded even with other guild members. They are personalize to one persone.
Another Example: Doing a job for the Kingdom: If you are a warrior or guard or whatever. You can do a job of guarding the castle, spy on kingdom, steal from kingdom, do some damage,etc. While doing this job you will be paid a decent ammount so the player ould be like: SWEET DIAS! or something like that. And so on...
I have some other ideas but im not bothering to post them if your not interested. Yes it will be alot of work but the Kingdoms would be popular again
Questions comment ideas?