[AlexH]

There are special areas dotted around the overworld which can be taken over by each kingdom.
Could be things like shops etc. If you making kingdom funds again also buildings like joinery which a kingdom would need to own to build things.

Using the shop for example. Say Zormite own it. They could buy bombs, arrows or whatever there and say it costs them 10g for 20 bombs for example. All the other kingdoms could still use the shop but it would be more expensive for them to buy goods at that shop. Say 10g would only get them 10 bombs.

If you plan on having destructable NPCs like guard towers etc for the kingdoms main area they may need to use the joinery for example. Again both kingdoms could use it but again the kingdom which owns it would get a discount in price. In addition to that they would also get better quality building. For example it's health would start at 100% whereas if they do not own the building it's health may start at 70%.

I guess that kind of system could be used with other buildings too but I'm too lazy to think of some more right now.

The buildings would be defended in kingdom battles. However more arenas would need to be made so it adds to RPing. As if they are trying to take over a shop they magically appear on some islands to fight for it. They should be able to fight inside a building similar to the building they are trying to capture, except with more space and weapons. These events would need to be arranged by some sort of RP person so that the players can't just chop and change it to their liking.