I proposed it and implemented it in my modmod 6-8 months ago. It was easy to implement, though I think I made barbarians play settler and other AI's play chieftain. It did of course require some rethinking and reworking of all the modifiers throughout the difficulty line. I'll probably resume work on the modmod in about 2-3 months, when it gets more refined, I would expect some discussions about what parts of the modmod might tricle into the main mod. I think it used to be replaced by almost all housing after and including stone huts.