I'd be happy with any of options 2-4 at a high level.
Thoughts on potential options
My preferred solution would probably be non-cheating AI being matched with people who join the 1v1 queue and fail to find a game after a couple of cycles, with an option for people to opt out. Players would only get matched with an AI within a certain rating range (say +/- 300 of that AI's rating), and also would only be matched if their last game (or last x games) was against a human. New players would also fight against an AI as one of their initial 'rating assessment' games (to hopefully give a better new player experience to the 1-sided initial games that can happen with the current system). I'm guessing this falls into option 2.1.
A variation on the options is to also have the AI implementation done temporarily (i.e. for the option 2s, you could have a week each month or quarter where AI gets added to the pool, a bit like how mapgen was featured for a week).
If option 4 was done (separate ladder) then I'd prefer it to have both AI and AiX; if it was done for just 1v1s against the AI then it could be done as a 'AI Challenge' button since a game could be created as soon as you click on it, with the goal of trying to get the highest possible rating. While the rating given from this wouldn't be as useful as under options 2-3 it'd still be of some value.
Potential benefits
As to some of the potential benefits I can think of initially from these options (which will vary depending on the option):
- Rating for AIs [options 2-3, and to a lesser extent 4] - this helps people select the appropraite AI for their skill level in custom games, and gives a better sense of their own skill level if they beat said AI. It also helps the AI developer get a sense of how strong their AI is and incentivises them to improve the AI further (in order to improve their AI's rating).
- Better assessment of new player ratings [options 2-3] - with appropriately rated AIs, it should be possible to give a better 'new player experience', by having new players fight an AI in one of their initial matches which is likely to provide a gentler introduction than being crushed by a much higher rank
- Decreased matchmaker wait times [options 2-3] - allowing AI to play to some extent effectively means more 'players' are playing matchmaker at once, so you wait less time to find a game.
- Potentially increased matchmaker popularity [options 2-4] - PvE is very popular on FAF. Depending on how the AI was implemented, it could lead to more people who would normally only play PvE trying out PvP (note that it's also possible for the reverse effect)
- Improved AI developer feedback [options 2-4] - AI devs would be able to look at replays against their AI to see how their AI performs and identify improvements to make, resulting in better AI for FAF.
- Improved PvE experience [Option 4] - I suspect many players aren't even aware of the various custom AI available in FAF and assume that the best AI we have is the Sorian adaptive AI. A queue that highlights the different AI with appropriate settings could give an easy way for particularly new players to jump in and play a PvE game without needing to decide on an AI or map. Meanwhile having AiX featured would allow PvE players to compete with each other at who can do the best against AI (since each AiX would have a rating, in turn allowing people doing this option to try and gain the highest rating by beating the highest AiX modifiers), and in turn give the AI developers clearer examples of flaws in their AI to be improved.
Potential disadvantages
There are also potential drawbacks from each of the options. The main ones I'd see are:
- Time and complexity of implementation - I dont know enough about what would be involved to say which one would be easier/harder. All options would I expect require a significant amount of time though.
- Potentially decreased PvP playerbase [more of a risk with option 4] - i.e. with a separate queue there's the risk people who would have queued for PvP 1v1 queue for PvE instead
- People being forced to play AI when queuing for PVP [option 2-3, depending on implementation] - if there's no opt in/out option for playing against an AI then you could end up with someone who doesnt want to fight an AI getting a game against an AI (that they then lose rating for if they quit rather than playing)
- Increased wait time for people who opt out of AI games [option 2] - e.g. player A joins the queue, and gets matched with an AI. 10 seconds later player B joins the queue. With no AI they'd have been matched with player A, but now they dont get matched. However it's debatable if in aggregate this would result in an increased wait time (if player A would have given up on queuing then the AI could result in more people queuing over time, meaning both players benefit)