With the switch between cultural assimilation and land purchases, the borders are now essentially fixed between varying powers and civilisations. However, these borders cannot change without the use of a Great Artist or a war that results in one or more cities being annexed/puppeted/razed, the former being a sometimes poor use of a GA and the latter sometimes being undesirable. Perhaps a new system of territorial ownership and territorial control could be implemented? For instance, a tile would be given a coordinate or a name, the coordinate being assigned and the name being automatic or input, and during negotiations a player could offer gold per turn or lump sum for a particular tile from another player. While this may or may not be realistic, it happened quite often during the imperialist era, wherein European powers essentially paid unfortunate African and Asian states small amounts of money as "lease" for territory, such as leasing the port city of Qingdao for one hundred years. Not to mention, of course, seizing of port cities and extraction of concessions. Otherwise, during a war a player that advances deep into enemy territory would "occupy" tiles, rendering them unproductive for the owner civilisation and making capturing of cities easier due to the lack of workable tiles. Starving cities would suffer from a defence malus or some other effect that can be detailed at a later date, and the diplomatic AI would recognise such an occurrence and offer a few tiles on the map that would be shown if the cursor hovers over the tile names in a strategic map view-style. Occupied tiles would generate partisans or rebels every so often for the owning civilisation so long as the civilisation in question maintains a positive happiness rating, thus creating the incentive to end wars quickly lest the invasion force be bogged down in a quagmire of resistance. Lastly, occupied tiles can eventually be directly annexed by the occupying civilisation if n turns have passed, thus representing the forceful signing of an unequal treaty or what have you. Ideas?