There is a lot of Twitter content out there. Too much for a single instance to proxy. I believe there are projects to mirror specific Twitter accounts to a (personal) Mastodon server so you can switch apps without needing two apps. I'm not sure what the implication would be for privacy/data usage regulations if you open those messages to the public, though; blindly reposting everything may actually violate data privacy laws (yes, even if that information is publicly available).
Engagement with the audience also is a significant factor for making social media enjoyable. A read-only mirror of Twitter would be very boring, because you can respond/tag/whatever you want for all eternity, but the Twitter authors would never notice.
Such a system would work for people primarily using Mastodon that cross-post to Twitter; you could add Twitter replies to the Mastodon replies and get a mixed content stream (that Twitter users might miss half of when discussions respond to as-of-yet unproxied messages).
Interestingly I started using Twitter as a write only medium, which means I didn't have any interactions there with anyone. This led to the subscribers stagnating, everyone who already was subscribed stayed subscribed but no new people would subscribe for years.
Nitter exists and it is open source. Why not add a mastodon API to it?
The existence of such a thing in no way has anything to do with existing mastodon instances TOS / acceptable use relationship with twitter (if such a relationship even exists).0
Engagement with the audience also is a significant factor for making social media enjoyable. A read-only mirror of Twitter would be very boring, because you can respond/tag/whatever you want for all eternity, but the Twitter authors would never notice.
Such a system would work for people primarily using Mastodon that cross-post to Twitter; you could add Twitter replies to the Mastodon replies and get a mixed content stream (that Twitter users might miss half of when discussions respond to as-of-yet unproxied messages).