Personally, I would like some more flexibility for nations allowed in a league. Unless I tweak the files, I may be scouting African players in 1901 (when really those nations should be colonies). Setting foreigner percentage to 0 is an imperfect solution, because I might - in 1901 - want to be able to add Canucks (who were actually Brits at the time).
Actually, what I think I would like is a "historical nations" database, for various times during the 20th century. E.g. you would have the GDR and USSR if you play a league in the 1960s or 70s, or Ottoman empire if you play before 1919.
I do understand, though, that this is not very high on the priority list except for strange history nerds with ideas for international "what if" leagues.

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One strikeout is a tragedy, a million strikeouts are statistic.
- "Stallin' Joe" Dshugashvili, Manager of the Moscow Red Stars 1922-53