I see at least two things that might be necessary but not yet implemented: end-to-end encryption for private messages and fine-grained moderation controls. The first problem is really difficult. I have some ideas on how to approach it, but Fediverse as a whole is very far from supporting cross-instance encrypted chats. The short-term solution is to limit private messages to one instance, in that case a user would need to trust only one instance admin. The second problem is easier, I will be working on it.