I vote for Blaze2. Retro-compatible with Blaze, but with fancy new features.
That would be great, and I don't see why they wouldn't.
Do you have more specific examples? Vue has a lightweight virtual-dom implementation, but with lots of possibilities to manipulate the DOM.
We could, there are Tracker integrations for Vue like the one I made and I use in the PoC.
The Vue backend could use vue-apollo.