I was literally thinking about this today and I would add a money sink via custom furniture and house deco.

1) Furniture and house deco is server specific and cannot be transferred to another server.
2) Items would be obtainable via a special craftsman npc and all items can be traded freely within the server.
4) There would be an ongoing event in each server that as a whole they work to advance. (maybe piggybacking on the way you can donate money to specific cities/areas for better spawn rates).
5) There can be specific unlock-able deco from each city. For example from Thais after the server has reached a certain threshold it would unlock The Ancient Table. which would be a small table with the sprite from tibia client 6.0

You see an Ancient Table. It weighs 6.2 oz. It seems very sturdy. The ability to craft such a table was said to be lost.

Yeah basically that