This is a really good idea. My nomadic start so far uses Mongol Camps from the database (I think originally by Bhuric, but I might be wrong) to do a similar thing. But I had not considered the "cannot reveal new tiles" feature. That would certainly force units to stay near the camp/tribe. It'd also be pretty easy to do through python, I think - just use a promotion, then under "canMoveTo" or whatever the equivalent is in EventManager.py, check if a unit has the 'Can't reveal tiles' promotion and prevent them from moving if the tile is unrevealed.