Moneys!

[caravel]

OK, back to the topic, does anyone knows is this possibility for AI.

The AI would be partially unable to exploit such a strategy - even through modding. This is mainly because the AI lacks the disband/destroy capability (the AI is unable to manually and selectively demolish buildings and disband units). Disband/destroy is another feature that I regard as an exploit (but many do not). It was introduced back in Shogun Total War: The Mongol Invasion expansion and has been present in all TW games since. In my humble opinion it's a bad feature and does not add to the gameplay experience.

If you want the AI to gain more florins from taking provinces, then provinces themselves need to be better developed as a whole. One way to do this is a big cash injection for the rebel faction. This is very easy to acheive (in VI) by adding a generous "cathedral income" to the two unused tavern and brothel buildings (in VI both the tavern and brothel are replaced by the upgradable "new tavern" and "new brothel"). Both of those buildings are rebel only so no faction will be able to build them and they will be automatically razed once a faction takes the province. You can set the tavern and brothel to cost 1 florin and 1 year to build, which ensures the rebel faction gets the pair built in every province ASAP before it goes into the red. This way the rebels will be developing their lands in sync with all other factions, instead of stagnating for centuries. It can also mean lots of annoying rebel assassins and spies running about.

Another exploit, before I forget, is the in battle "kill prisoners" button - this is also something that the AI cannot use at all. It gives the player the flexibility to avoid the in campaign ransom offers that follow the battle. So if you capture the enemy's 9 star faction leader, you get the option to kill or ransom. The AI only has the option to ransom and see if it is accepted or not.