The best plan I've seen is this proposal[1] by Saagar Enjeti, in which Twitter is repurposed as the worlds best customer service hotline. Charge people with large follower base for their followers on a scaled basis... with a large free tier to help out those just up and coming.

Get advertising completely out of the business model.

[1] https://www.youtube.com/watch?v=zwOm4QOZN9k