I'm not sure. On the one hand, +75% for military units IS a lot; you can go on a warpath and overwhelm a neighbouring civ before they can get strong enough to defend. Extra happiness per military unit and no culture flips are nice to have as well. Very early in the game, you might have fewer tiles getting worked, mostly those with resources, so the 'no cottage growth' item is less relevant; the GP malus hurts more, but still, it can happen that you expand early and snowball from there, penalties nonwithstanding. Progressive civs getting attacked by a bigger, military-oriented neighbour should (depending on the situation) probably switch to and from Autocracy, rather than staying in another civic, particularly in those situations where they're holed up in their cities, their countryside pillaged. The same could be applied viceversa; maybe a Progressive civ/leader could consider going Autocracy for a few turns, spamming units for a quick conquest and then switching out of it for peacetime. Merchantilism's bonus for water units is a similar case to this; water units can't conquer cities, so there's that, but what I mean is that it's a situational but potentially game-changing feature, which the AI may or may not use fully to their advantage. So, I don't know, really. Good to hear that I might see some late-game AI autocracies.