I've been working on modifying the very fun, free mobile games: College Football Coach, Pro Football Coach and College Hoops Coach lately. The games are fun text GM sims but have fictional teams and leagues.
The Pro Football game does allow you to customize team names and rosters which I shared in a previous post my 2017 update. It still had fake league names though. A simple edit of the code fixes that.
College Football Coach is actually open source on GitHub. I got the source code and have been playing around with it. I've so far modified it to include real conference names and teams. I would like to work on it some more if time permits.
Finally, College Hoops coach is the most robust of the three. The team names are actually called out within a XML file and that was actually rather simple to change. There are some other items, I want to tweak, but I haven't gotten around to digging into the decompiled files yet as I don't quite understand smali yet.