1) Have 5 levels to a fighter's location. City, State/Province, Region, Nation, Continent. (Probably have a database a cities, assign a fighter a city, and from that get the other locations).
For instance, in the database you could have
Philadelphia, Pennsylvania, Atlantic, USA, North America
Assign a fighter the city of Philadelphia, that would "fill in" the other 4 fields. This would give us a much better image of where a fighter is from (and allow the other features on my list). Include other factors for flavor, or to effect money issues. For instance, a city might have a very good economy, thus fights held there would generate a larger gate, etc.
2) Allow us to assign World, Continent, Nation, etc. to an Organization. And then we could have Organizations rank all of the champions that are below it. WBA would be a "World" Organization, and thus they would with list NABA (Continental - North America) champions, EBU (Continental - Europe) champions, USBA (Nation - USA) champions, etc. But not other World organization champions (IBF, WBC, etc).
This way, if I wanted to create an Australian organization, all I have to do is assign it "Continental" and "Australia" and that would be it. I wouldn't have to go through all of the fighters in my database and assign them to "Australia" for their 2nd group.
Also, I might want also want to make something like "Atlantic Boxing Association" or whatever. This (along with the City-State-,etc from above) would let me do that. Just Pick Region - Atlantic and I'm done. I wouldn't have to assign fighters to an Atlantic 2nd group, which then causes me to take them off a possible North America group, causing a bit of a problem if I have a North America organization.
3) Give each fighter a "Reputation" rating. Same levels as above, City-State-Region-Nation-Continent. When the auto-scheduler looks for opponents for this fighter, it could try to match reputation and location. For instance, a fighter with a reputation of "City" (and they are from Philadelphia), the auto-scheduler will only look for available fighter from Philadelphia.
"But if there are no fighters there? How does he go elsewhere?"
Well, a fighter with a "State" reputation will look for available fighters in their state, including fighters that have a "City" reputation. You could allow the game to go one or two levels lower to find opponents for a fighter (but cut it off at 1 or 2, so that we don't have World reputation fighters going all the way down to City level fighters which would create very unrealistic fights).
Popular prospects starting out would probably start off their career with a Regional or State reputation (1, so that they avoid any chance of getting stuck fighting more mature fighters if they are from a very low populated city in the game, but mostly 2, because in real life they do.
).
As a fighter moves up in the rankings, have dramatic and exciting fights, beat fighters with higher reputations, their reputation could go up. However, I don't think they should move down in reputation. Once a fighter reaches a certain level of reputation, he pretty much stays there. Holyfield, despite how badly he has done the last several years, still is known worldwide, as is Tyson. We don't want some silly thing where a fighter known nationwide suddenly drops to City level because he hit a bad streak. Once he's known nationwide and is fighting at that level, he pretty much stays there.
You could also have a fighter's reputation effect rankings. Have it be a modifier. This could let us have situations where a fighter stuck at a reputation of Nation does not get ranked highly and, like in real life, has to wait it out for a fighter with a higher reputation gives him his shot (or put together some nice wins on TV of a PPV undercard to move up). Like above, we don't want unrealistic situations. A guy not known, at the very least "Continentally", does not get ranked in any worldwide Top 10 or 20.
4) Reputation, along with "Draw Power", would also ideally effect the amount of money a Fight Card generates. A Main Event featuring two Regional fighters wouldn't generate a big gate, regardless of how high their "Draw Power" is.