OK, seeing as I can't do this myself....
Can you please create a league comprising of the six former Yugoslav republics (Serbia, Croatia, Macedonia, Bosnia, Montenegro and Slovenia). Each division should have 18 teams and there should be 5 divisions (Or more, if there are enough teams and it can be done, but I'm ok with 5) Teams should be placed into the divisions based on reputation. There will also be a cup competition which will include all teams from these divisions (or maybe more teams, some of which aren't in any of the divisions if that can be done) I'd like to keep the six national teams as they are and have the clubs produce newgens from the country of the city that the club is based in. I know you said that new players coming in will gain the host nation's nationality but if that can be avoided, that would be great.
So, the league will be based in one of the six republics and that is fine as long as the actual competitions from there (as well as all the other republics) are removed and replaced with this new one. This new league should now have a different Uefa coefficient than the host nation did (you can set some arbitrary value to these or combine the values from the six nations, or I can do it myself later). Any other info that is necessary and needs to be done a certain way to make it work, let me know and I can tell what I would like. Otherwise, if it's not critical, you can leave it for me to do, I don't mind.
I have made an xml file of what I think this should look like, but when I try to start a game with it, it crashes while it's setting up the database. If you would like (and you tell me how) I could upload it and you can tell me where I'm going wrong. I didn't include a lot of the details like prize money and such because I thought those would be easily added in once I get the oevrall structure. Also, I tried to do it by making a new nation but since I don't actually want a new national team, I don't think it's going to work.
If you think you can make this for me (at least the overall structure that will make it work, I can fill in tedious details like prize money and such myself if you like) and you get what I mean, great, but I understand that it might take a while or I might not have explained it well. So if you would like more details, let me know. If you want to see my xml file, let me know. Otherwise, if you have any other ideas as to why this is not working or advice on how I could do this, all would be much appreciated.
Thank you