The problem with kingdom structure, rewards, management, etc. etc. has been voiced numerous times, not only in the thread you linked, but here:
and here:
and here:
Literally nothing has been done to kingdoms since the beginning of early access in March. At this point, I really hope they just rework kingdoms entirely and that it gets a robust update before launch. Currently keys are pointless, Food is king but mostly unable to be spent, and active kingdoms are punished daily. Virtually everything about the current kingdom structure is bad and needs to be rethought.
Until they actually update kingdoms, maintain a kingdom of ~15 players.