Have seen quite literally dozens of versions of this idea over the years.
I'm sure this is well made and a fun project to develop, but I just don't get the fascination with this idea of desktop OS mimicry in a browser tab.
Why not build (complex but specific) SaaS applications that just leverage OS designs paradigms on the frontend (taskbar, windows, notifications, desktop, icons..) inside the same tab?
What if the OS-like apps were open plugins that will augment that SaaS?
[edit] here is an example: Imagine an alternative OS-like interface to HN that is plugin-based. You can add themes, or apps like messaging between HN users (in different windows), keyword-based and comment replies notification (a la Action Center)...
it is like HNES [1] on steroids.