Instance-bound (I'm assuming federation-wide implementation would be extremely difficult) shared user lists primarily associated with the creator's account. A rudimentary administrative privilege system (read-only, can add, can delete, etc.) would be ideal. Perhaps users could be offered an option to follow the list and another to follow all users in the list.
From my perspective, lists are the most powerful curatorial tool on the social web. The common obstacle for new Mastodon users in "finding accounts to follow" would be offered a substantial remedy, I believe, in public-facing shared/collaborative user lists. A view showing basic metadata about the list (description, list of collaborators) with its own permalink might offer new users significant context.