A smart email import mechanism that could parse the hideous mess and repetition in a history of email conversations and turn them into neat flarum discussion threads while set up accounts and emailing people to let them know.
It would probably need some staging mechanism to approve things as it would be very fragile but I've got a community of about 50 people currently chatting by email about really important COVID-19 research and it's all hidden away in email instead of in a public open science forum...