Some interesting research being done in this thread, the upgrades possibilities are intriguing. One problem I've been having is the seeming impossibility of getting rid of a building in an individual region after it's been built, short of the player manually destroying it for non-hinterland.

Has anyone found a way to destroy a building in an individual settlement without player interaction? Or even just throw it back to level 1?

I've tried both a number of variants for the set_building_health console command, but no matter how much health hits you lump on the building can still be repaired. Furthermore I've tried making the upgrades of buildings circulating, so that under unachievable conditions the last building can upgrade into the first, effectively 'destroying' all upgrades. The create_building command doesn't seem to take kindly to being told to create a building which is lower on the list though, from cursory testing. And then there's click simulation, but I'm not aware of any way to select a specific building in the ui, so that's pretty much a dead end.

This might not seem that useful for buildings which represent well, buildings, but it's important realistically for buildings that represent anything else, such as policies. This is especially true in games with multiple human players. For instance, if you wanted to represent a regional 'laws' system and Rome captured a Gallic settlement, you wouldn't inherit the development of law in the region, as Gallic and Roman law differ and need to be built up separately.

One fix is of course to use multiple building trees for different factions or culture groups and just null the bonuses on the other ones. But the problem is that uses a lot of building trees, which to my understanding you can only have 128 of. Another solution would be to upgrade it to an unused 9th building which is essentially "Loot" and has no bonuses, which would prompt the player to destroy it for the monetary return. Both of these are clunky solutions though, which is why I'm curious if anyone has solved the problem of destroying(or at lead "downgrading") individual buildings in specific settlements.