I still would like any movie adaption stick to Stan and Jack's Fantastic Four. IMO the Michael B. Jordan and Kate Mara version of the Storm siblings in the failed movie shows why it doesn't work. But it could be the actors didn't try very hard to make an emotional connection.
As for Namor being derived from the Mayan culture, that just doesn't make sense to me. The Aquaman movie was somewhat successful with the depiction of a kingdom under the sea but it showed it's limitations too. What might be more successful is what was done in the Kong: Skull Island movie. Let the "Atlanteans" or what ever they decide to call Namor's people be a lost civilization discovered on an island. The flashback would take place in the 30s pr 40's and show a group of explorers that discover the island. Of course the leader would be Namor's human father Leonard McKenzie. This culture would be advanced enough to see the dangers of being discovered and come up with a technology to make the island undetectable.