There was a recent massive downgrade in the AI model and I assume it's because mediocre players were sad that they were losing to the expert level. So instead of removing the old one, how about offering the old versions as selection options when setting up a game? You could leave them as version numbers or give them cutesy names with sequential first letters like Android does with Oreo.
But please give us a way to go back to the last version (or other versions) of AI.
And this would also open up the options for some versions being more aggressive, more defensive, more motivated by protecting continents or knocking out other players, etc. etc.