I suspect this has been requested before but my searches didn't find anything (probably just searching for incorrect terms.)
It would be amazing if rclone could detect api/download limit/misc issues on a remote, specifically with union remotes, and exclude that remote for a timeout period or some similar mechanism.
I've been trying to automate this by grepping logs and executing scripts based on certain text triggers. It works just "okay" but it's not as accurate as I'd like and unfortunately I've hit my "coding" skill level limit (translation: I googled and mashed up a bunch of things in a very, very ugly way.).
Thanks for your consideration and thanks for making and developing this awesome utility.
And I just a idea for 3) combined with a random search policy, you don't even need to see if file exists in the remote if it fails to open, since you have already that. can recycle that to cut api requests