I know this is usually not the best strategy for coming up with side projects but for me it's just always about solving my own problem. The downside is that I'm solving the problems mostly fellow nerds have that they usually want to solve themselve instead of paying someone to do it for them. What I'm trying to do more actively now is to always keep my eyes open at my day job and try to spot problems that are solved…
Not at all a critic of your idea/tool, but I am surprised (this probably shows how old I am getting) that there can be (many) people willing to spend 10 $/month for a weekly report of twitter bookmarks. Maybe people working in the media or that however somehow monetize their twitter use?
Our main goal is to streamline curation and consumption process. Apart from bookmarks digest, it can also connect to third party apps part of creative workflow. Right now, we have one-for Notion to auto-sync bookmarks and for Zotero to auto-sync research papers when research scholar bookmark a tweet with a journal/research paper in it.