I truthfully don't think this bridge will work long-term because it's rather clunky for the end users. I think mastodon needs an integration built into their platform so instances can have the choice to turn on a two way atProto connection that creates accounts under the instance identity and writes and reads post to atProto.
Bluesky doesn't need to adjust anything as they'll pick up anything written to atProto.
While they definitely do this for handles I'm pretty confident this is also done for DIDs (Decentralized identifiers) and it doesn't provide a solution if you lose your domain. I think Bluesky (Appview) specifically gets around this by also tying your DID:web to your DID:plc, in case of domain loss. So I think it exists on the protocol but they don't automatically utilize the decentralization for end-user experience(domain loss) but other appviews can. But I could be wrong.
https://atproto.com/specs/did