Firefox is dead to me – and I'm not the only one who is fed up

Isn't it technically possible to split browser functions so we can recombine as we like? - i.e. separating the rendering / js engine from everything around the side - managing all the tabs, bookmarks, cookies and passwords, workspaces and sessions, mail, notes etc. In my case, I like the workspace structure provided by Vivaldi, but don't see why it has to be built on chromium browser. Anyway as a developer I need to test against blink, webkit and gecko, so would be nice to swap them within the same user interface structure.
By the way, I develop a "javascript-heavy" web-app (interactive climate model) and it seems to be working fine, and fast, in firefox, so I'm not convinced by complaints in the article.