[2022] Idea

Capturing an enemy city that has a building in its territory that you don't have the technology to build should grant you that technology by reverse engineering the tech the other tribe used to build it. For example, capturing a city with mines should give you mining if you don't have it.

This incentivizes going down the farming/windmill branch to get the destroy building ability to destroy buildings in sieged cities to prevent the tech falling into enemy hands. It also incentivizes, as the capturing army, putting units on key buildings to prevent them from being destroyed to ensure you get to tech.