Tinkering with social media is not a good idea. Current social media business models should be completely banned, for everyone.
A social media platform should be forced to operate as follows:
1. On the main timeline, it must only show content from people or groups that the user explicitly follows. The only way you should be shown content you don't follow is if you explicitly search for it.
2. Content must be shown in reverse-chronological order, so when you see something you've seen before, you know you've also seen everything after it.
3. Advertising and sponsored posts should be prohibited.
4. The only acceptable way to raise revenue should be subscription fees. Facebook makes around $3 to $5/month per user; that would be an appropriate range of subscription fees. This would make bot armies economically infeasible.
Regulating social media in this way would eliminate 95% of the harmful aspects. It's a simple matter of product safety regulation.