Yep, the timeline is a pair of glasses. I drew my quick sketch to be familiar to those using Mastodon and similar timeline UI’s. You can go any direction you want UI/UX-wise. And here we get to a point where the analogy becomes strained. It is the data you receive from the Fediverse that determines your “worldview”, the completeness of your overview. The UI/UX are then more like the colors of your glasses, that allow you to see the same world in different colors.
In that timeline there are custom types with their own dynamic widgets delivered and still managed by 3rd-party providers, and you don’t have to beg BDFL’s on an app-by-app basis for 4 years to please include native support for your custom type. Which, btw, understandably these BDFL’s are reluctant to implement. It is simply not their “core business”, which is their own app and its use case / objectives.
Update: Some related thoughts on this in Thoughts on Actor Model versus Fediverse - #4 by aschrijver