Faith cost of spreading opposing religious buildings

[Workerspam]

How much faith does it make strategic sense to spend in order to spread an opposing religion's buildings to your cities?

The general scenario is you are the leader of a religion and an opposing religion takes hold of one of your cities. If that religion has a building as one of it's follower beliefs you can then buy it in that city. Going a step further, you can buy an Inquisitor and Missionary(s?) to spread the opposing religion to other cities in your empire to gain use of that building. Depending on the situation of religion in your game you might have to follow up with an Inquisitor and Missionary of your state religion to revert the city back.

I did this once as Tradition Arabia to gain a Mandir in my capital (I forget whether it was also my holy city and if that would matter). The issue is it is a faith intensive operation; without discounts you're spending 3-5 times as much faith to gain 1 follower building (2-3 times if it's a two follower building religion and you build both). But there are situations can alter the equation.

In my current game I have both Fealty and Pacifism (reducing the faith costs and lowering the cost factor to 2.4 times) as well as Sacred Sites (adding 3 tourism for each faith purchased building). My religion has taken root on my island; England and most CSs follow it. Washington is the only other civ on the island and his cities occasionally flip to my religion so there's no worry of losing a religious war. He managed to missionary bomb one of my new Pioneer cities, granting me access to his follower building: Pagoda. My cities only have the 2 religions present; while there are 4 additional religions in the game (Large map) I don't anticipate any of them making their way to my cities.

I ended up not pursuing the spread strategy (I did send an inquisitor to another Pioneer city but forgot it only purges the heretics; my city ended up with 1 follower of Washington's faith and not following any religion). If it was a stronger building (Synagogue, Mosque, etc.) I might have, at least to my stronger cities.

I'm curious what others think about this. Do you never consider spreading an opposing faith for their buildings? Only for strong buildings in your capital? Should I have converted my cities to gain the 2 yields and 3 tourism in all my cities? Or do you consider this an exploit (since I don't think the AI is capable of this type of religious manipulation)?

 

[Omen of Peace]

I've tried it, for fun. I think it's often not an efficient use of faith: as you point out, it can be costly to buy a bunch of Missionary and Inquisitors to spread & clean, plus the cost of the building.

It can be useful in very specific cases, as you point out (with discounts, if you're swimming in faith with nothing to use it on for a long time, ...).
It's such a niche tactic that I don't think it's an exploit.

 

[Galbias]

I've done it before. The yields and/or other benefits can be nice but the religious pressure that the buildings generate tends to end up generating a bit of unreligious happiness on top of the costs.

 

[Owlbebach]

I did this once as Tradition Arabia to gain a Mandir in my capital (I forget whether it was also my holy city and if that would matter). The issue is it is a faith intensive operation; without discounts you're spending 3-5 times as much faith to gain 1 follower building (2-3 times if it's a two follower building religion and you build both). But there are situations can alter the equation.

I've tried it on higher difficulties, usually not worth it. But it might be worth getting a Mandir or Synagogue or maybe Mosque in your capital if you feel like haaven a lot of faith.