So was I. But I suspect the amount of work for the GM didn't become apparent till it was too late. The Pathfinder Kingdoms campaign is a combined roleplay/management campaign for one group running one barony. I suspect trying to manage this for multiple groups was just too much work.
Though I could have suggested an alternative way.
A single large barony subdivided into however many regions PC's want to manage, but located fairly close to each other. Advisors handled much as now, kingdom rules used much as now for the 'knights' holdings.
The single barony has no baron or build orders, but has the 3 or 4 or wharever Knights (PCs) ruling it in council. Probably not much to do at barony level initially as all building takes place at 'knight holding' level.
Roleplaying is where it makes the difference. The GM doesn't need to think of seperate adventures for each realm, we are all close, and mostly based in the Baronies capital rather than our own villages. So we can deal with issues as a single group when a roleplaying situation happens.
This reduces the GM's workload considerably, as turn management isn't a vast amount of work.