M2TW Kingdoms (Brittania Campaign) is like that-- it has "culture" vice "religion", so until your culture gradually takes over you can build "native" units. Not sure about the other Kingdoms campaigns.

There are also several mods like "Stainless Steel" and Broken Crescent" that have it to varying degrees. There's a guy named Point Blank that has a "Real Combat/Real Recruitment" submod that seems to be used by many base mods to implement Areas of Recruitment.

If you go to "twcenter.net" and search you will find a lot of stuff about this subject.

Cheers!