I might be missing something, but all of these seem like solvable problems. They are mostly data transformation problems, AFAICS.
For example, it seems fairly trivial (especially relative to the payoff of doing so) to map a Bluesky feed to a key pair in Nostr to make it easy to consume that way.
Indeed, this could be a monetisation vector for relays able to offer more advanced interoperability features.
It’s not like the problems of integrating with, say, Twitter, Reddit, or Facebook. There are far more obstacles to that than merely transforming data from one shape into another: violating terms of service, lack of APIs, KYCing, etc.