AIs have a lot of variability in them. Markers, competency, type of games they work best in, ability to work with mods, and so on.
The problem is FAF has a ridiculous amount of complexity for getting this stuff set up in a way that provides a decent new user experience. If choice is given to the user, they need to be simplified down to what is pertinent without overloading the user with insane amounts of information.
It doesn't help that a lot of new users play with parts of FAF that there just isn't that much institutional knowledge about (40x40+ maps, gigantic modded games).
I'm imagining something like a campaign screen where you can pick some list of 12-15 curated maps, it has an easy/medium/hard AI curated for that specific map, and you might have the ability to pick between 3-5 variants of game modes that add mods for a specific experience while also not causing desyncs or crashes by being together. A few of these maps can be survival scripts, even. The point is to get people to get a sample of everything pve that is already curated so they can find out what they like.
In terms of campaign, stuff should just give more of a sense of progression. The missions are haphazard and it's impossible to feel any story progression when you go through them. Beyond that, I mostly feel like leaderboards with replays become a way for players that are in it for more than just the first go through to participate in their own thing. The problem currently is desyncs and huge bugs being found in missions, but I would argue this becomes a feedback loop for game/balance/coop team in turn and there just needs to be a way to reset leaderboards after (significant) patches.
Some missions also just need to be reviewed as balance patches happen because things like the Aeon lab change suddenly make them way more insane.
You can have people do things in custom games, but that's just the wild west and not supposed to be the showcase for a new player. Rather it's for experienced people that know they want a specific thing.