There are many items which have received different ratings through subsequent prints. For example, this was typical when PEGI was formed in Europe, but there are several other scenarios as well where it's occurred.
Sometimes, the rating can be used as the entry name descriptor. So, in this case, the entries would be formatted something like this if using that formatting choice:
Lego Marvel Super Heroes 2 (ESRB rating)
Lego Marvel Super Heroes 2 (SMECCV rating)
But, since these items would be surrounded by other non-Mexican ESRB releases in the same category and because there is other varying information between the two such as item numbers, I would personally suggest using this method for the descriptor. So, if using this formatting choice, something like this could be used:
Lego Marvel Super Heroes 2 (3000074524)
Lego Marvel Super Heroes 2 (3000087139)
Either way, it is important to clarify in the Description field where these items were released, since TLD information would not be present in the entry name.
We are not concerned with how a game was rated prior to release. Many games have rating information updated before releasing, but we are only interested in the ratings that individual physical items feature once published.
You've been an incredible help to the database in submitting MX entries. Your work hasn't gone unnoticed, and it's certainly appreciated.