I have done what hide-my-email alias now offers for years with normal email aliases and a catchall.
But I would like that to be integrated in proton mail directly so that I can enter an email there to be whitelisted and not have to rely on a catchall. I generate random hashes for the names, and only when something sends to that name it should go through and not any other email too.

I also cannot see why there is a limitation on email addresses. There shouldn't be any real cost attached to it, and is the only reason I currently consider hosting my own mail server stack.