I wouldn't say they are the minority, keeping in mind they are the ones complaining about the lack of competition and they are the ones who made a suggestion about second teams.
In my opinion, Utopia/BB nation/Champs-Élysées/Mount Olympus is the best and the only option if this feature is going to be presented to the game. I know micronation teams are yearning for competition, but I would hate to see a foreign manager in my league. In Utopia's case, micro-managers could satisfy their needs, macro-managers could satisfy theirs. I don't see how Utopia could become less interesting in time, when you compete with highly acknowledged managers from all over the world. Anyway, that's just my opinion.
In an ideal world (Utopia, one might say!), perhaps you are correct. However, either with Utopia or separate structures or junior leagues or women's teams or college teams or regional teams or whatever else, any of those alternatives would require BB to undertake a massive addition to the database, creating new nations, league structures and perhaps special rules for players and whatnot. None of that is quick or trivial to implement. If they take the current route of allowing second teams in existing countries, they need to add code to flag secondary teams to disallow certain features, but they already have a league structure in place, the teams are already there, their games are already being simulated, etc. It's much less complex a solution, a much faster solution to implement, and frees up Marin that much sooner to continue work on stuff for the entire game world, rather than this nifty bonus for supporters.