If you drink some tea and switch ambitions, do you lose all the items you’ve earned along the way? Or could someone potentially play through all the incomplete ambitions to their current end and gain all the different rewards?
You lose them all (except first city coins, I guess).
I’d assume, for purely mechanical reasons, that it only takes away items unique to that ambition, and would allow you to keep any non-unique items gained during it. I very much doubt anyone who is at the end of their ambition has actually tested it though.