This is a good discussion here, so I take my chance to contribute…
For the framework decision:
I’m working all day with React and Redux in my daily job, so my preferred way to go would be React.
I did not yet work with Vue.js, but I heard a lot of it.
Array.map) to render the components without some templating or learning another framework-specifc syntax (like it was necessary in Angular).
Vue is easier for people coming directly from Angular I heard.
So it seems we are all agreeing on the fact that Angular is dead and we currently have React and Vue in the ring.
But things in the web are changing fast these days and since our new UI is still far away, I’m not sure when we should decide for a technology.
For the rewrite discussion:
I also don’t think we should embed any new framework in the current user interface.
So in my opinion what we need is a modern web application rewritten from scratch which does nothing than consuming a well designed API.
I don’t know, how it is possible to integrate a beta UI (like with the mobile UI) because it has to be all bundled together somehow and of course we should avoid having multiple UIs for a long time (like with the mobile UI).
Talking about components:
There are lots of nice component collections out there, so we can also think about using some of them instead of write all standalone components from scratch.
Even if you all want to hit me now for posting this link, in my daily business I often work with some of the React components of Microsofts Office UI Fabric React with some good components for a social network like the “Aspect Pickers”.
There are lots of other well-maintained component libraries out there, so we wouldn’t have to rewrite everything.