Honestly I think there's pretty gold interop already between lemmy and mastodon. There's some difficulty with seeing the the images from each other primarily and a way to reply to cross post / boost a mastodon note into a lemmy post so that replies are visible by the op in mastodon would be a killer feature, but everything else works.

I kinda agree that following mastodon accounts is out of scope for lemmy as the concept of following the doesn't make sense within the link aggregate concept. It would require lemmy devs to add a whole microblogging architecture for follows to make sense.