Twitter enables communication. This is my honest opinion about the platform so I think you’re spot on — the team should focus on this superpower.
But the solution you’re suggesting is wrong. Twitter should focus on acquisition first and retention second. It’s not as important if users stay, if they don’t come. And for them to come it needs to look outside of the platform, even into the real world. And if with the strategy approached they can also retain users, even better.
I sent a similar suggestion to Jack this morning, to focus on enabling conversations wherever the users are, and have everyone involved in those conversations following each other. This way they can keep the conversation going, but most importantly, convert to active users and understand the platform. Even something as simple as a comment system based on Twitter, that is embedded by bloggers, and publishers, and major companies that allow readers to be active in comments, would turn those users into active Twitter users and would enable those conversations to continue.