POISON AND WINE. Is sooo good.
Also, if you want ridiculous but entertaining There and Back Again.
They archive it here https://pinboard.in/u:dragonage_kink/t:character:alistair/
Now just scroll on down. Unfilled are prompts not yet written, but there are a lot of stories or starts of stories.
Also, I want to recommend that you don't sort by top rated on AO3. brace yourself and look at all of them. You don't have to read everything, but those that capture your interest. There are some seriously underrated stories that are amazing, but no one sees them because they aren't new.
Haha sure thing. It's called Elysium. Basically F!Cousland is brought up as a noblewoman with a courtesan's approach to diplomacy. There's some moments that are..uh kinda ridiculous but I really enjoyed the take on Alistair. Plus its complete!