I absolutely agree that key drops should be easy for alts (I gear several alts through delves).
What I would rather see, since we’re on the subject, is non-bountiful delves being the source of the coffer keys. Give us a reason to do those multiple times at endgame. I would like to see the delve system utilize the non-bountifuls for something, and it would make sense to find keys for treasure chests in another delve…in a delve.
Just an idea I’ve had and always kinda wished to see them implement.