actually couldn't you implement asks on fedi by having a public/unlisted post that just doesn't appear in timelines and is only sent to the non-shared inbox of the person you're are asking to? answers could be regular quote posts and because the post is public when the quoted answer post gets sent other instances will be able to fetch it then
i mean sure you'd need bespoke support on both the asker and answerer instance's side (asker would need to implement that specific visibility mode, answerer would need to separate asks from regular posts and put them on a list) but the pieces are already there