Couples suggestions: rather than Escudo MX (which is a bit awkward phrasing in spanish) you could use Campeón de Campeones which was the old Mexican supercup.
As far as age limits in lower divisions. Tercera (lowest tier irl currently) has had an U23 age limit for years, and it's very common for teams to field a lot of underage players. In case you want to take that into account.
Also wondering if you reactivated defunct teams at all, would be very cool to have Veracruz included at some tier in the structure.
File looks great regardless, will definitely give it a try!