Hmm. Yeah, I guess Civic Centers at least, maybe barracks and stables (anything military, TBH). Houses should just be capturable flat-out, same with any non-Civil Center civic or economic building. IMO fortresses should not be capturable at all, only destroyed (I know that doesn't really fit with history, but it would make the game more challenging).

To make it effective, some other ideas(features) are needed, such as damage from units with torches. Therefore, there would be fire damage, the capture doesn't necessarily need to be 50%, and not necessarily all buildings.

Han took years to develop.And yet it is not complete today.   The main idea dates back to 2010. https://aom.heavengames.com/cgi-bin/forums/display.cgi?action=st&fn=15&tn=28877 And debit in its own mod around 2014. https://www.moddb.com/mods/rise-of-the-east  

Is there a place where I can download this?

The only problem with that is it means that if you want to capture a building, you have to micromanage the attack. Often times you will look away from your invasion to train more troops or check on your economy, and that means any battering rams or catapults (the only units able to damage buildings quickly) can destroy a building you want to capture before you notice. And, it would be useless to code them so that when a building reaches 1/2 life (or whatever) to just stop attacking or move on. Plenty of historical battles involved surrenders without having to beat the building down, so there is another point.