Guidance on converting to multisite

I have an existing blog with bbpress and buddypress as well as a handful of other plugins. I want to convert the existing standalone site into a Multisite Network with the main blog/domain being almost landing page for the network and include links to the other sites.

The main reason for wanting to do this is to break the different topics into their own blogs while sharing user information, bbpress and buddypress across the network. The topics in the existing blog have some overlap but are an odd fit to cram into a single site. Also, the flexibility of different themes and plugins specific to that topic/blog. Essentially there would be six sites to start (example.com, topic1.example.com, topic2.example.com, topic3.example.com, bbpress.example.com & buddypress.example.com).

The overall end goal is to create one community with independent topics/niches within that network. That way a user/commenter can join the “community” and stay in their respective topic or can interact with other topics without having to create another account. This would all be restricted to admin created users being authors so no outside user could create their own sub-site.

I’m not sure if I’m over complicating things or not so I thought I’d reach out to the community for guidance or if my plan wasn’t feasible