I guess there is nothing much to improve upon with the current Civ5/6 concept. Either, the developers are heading back to Civ3/4 or we are stuck with what we see now. Since the AI shows absolutely no improvement (and the developer obviously not interested to spend any money on it), the goal should be to make the game easier for the current AI and not more difficult. However, all the subgames that have been introduced in Civ6 are making it more difficult for the braindead AI. Religion, Tourism, Civics with the many policy cards, districts with ever so important placements, builders that need to be constantly replaced, severe war monger penalties, crazy diplomacy, harsh movement rules. Nothing here which would make it easier for the AI to be able to compete.