I get the impression #Bluesky and #ActivityPub have such major design differences that a full gateway might not be technically possible.
From user account management through content distribution, as I recall the two systems have pretty different core design choices, so full compatibility through a gateway translator might not be possible.
Off the top of my head, it might be like an email to IRC gateway. Sure, something could (maybe) be kludged, but they are pretty different.
@volkris I think it would be much like the existing Nostr gateway at http://mostr.pub, where you can follow users from the other platform, see posts and profiles, etc. Obviously some things will be totally incompatible, as you've mentioned, so those features won't carry over.
It might be quite like various XMPP-Matrix gateways in that regard: most basic features work; with some patience you can converse with users from the other network, and sometimes join MUCs or public rooms.