I did this a couple of years ago, connecting from Puerto Vallarta. We had the options of leaving 2-3 hours between, or 5-6, so went with the latter and it worked well with a bit of a delay on the Aeromexico domestic flight.

Having an Amex which gives centurion lounge access was very helpful as there is one landside - the BA check-in only opens the minimum period before.

We had spent time in Mexico City at the start of the trip so preferred to have more time elsewhere, and decided a few hours in different lounges was fine to balance the risk of not making the BA flight.