If I remember correctly, EA MMA had a fighter share/DL type thing. That was pretty cool. But I wanna say the rationale for not bringing it into the UFC series was some sort of legal concerns with likenesses or copyrights. Something along those line. This is going back a decade though, so maybe/maybe not the reason when it comes to why we don't see it in current gen games.
Maybe I'm dreaming this up, but I even remember EA MMA had last names to choose from like "Little" or "Lydell" or something that would be announced in game like "Lih-tell/Lih-dell" (so your created Chuck Liddell had a somewhat legit intro). That fighter share thing was great. Since this game dropped all i've basically been doing when I play is CAF'ing to fill up the roster for a universe. It's taking forever even with archetypes.