Yep, it's a good idea, but as toh6wy said it sould be uncommon or even very rare. Otherwise, as soon as your Empire grow a bit big, you will be almost sure to get the ressource inside your border permanently.
Another way to avoid this problem will be to combine this idea with aaglo's idea. But the building sould be made obsolete by Civilisation Scientific Advances needed for stronger Ogre units, and make those spawed by a new building requiring ogre ressource, etc. etc. tec.
Originally Posted by aaglo
Well.
An option would be (and this would also reduce the amount of Ogres Only -forces):
- make ogres spawned from a building that requires the ogre resource inside city.
- give that building a ridiculous pay demand (like 110 gold or something like that )
- if this would happen, then we would be able to make the ogres very very very very strong (well, stronger than they are now).
But this is only hypotethically speaking - I doubt that this will happen with WH-mod