No problem. If it doesn't work out we'll think of some other stuff. Let me know what you ended up doing and how it went!
Sorta, but not really. In real life it is possible, as most nations have league, domestic cup, and a shot at continental cups like the Copa Libertadores (equivalent of Champions League) and Copa Sudamericana (equivalent of Europa League but not available in FIFA). From what I've read FIFA still hasn't added Mexico's domestic cup, but you could still win a treble there since Mexico, and Argentina, have two short league tournaments in a year and also the continental cup. Winning two back to back league tournaments is already very rare. Since Mexico changed to it's current format only two teams have been able to do it, UNAM and most recently Leon. So yes you sort of can win a treble, but not like in Europe. MLS doesn't participate in any continental tournaments.