Can I use the original Lego Boost to create the R2D2 droid set? My son has the original Lego Boost set (with Vernie, Frankie, etc), but is also a big Star Wars fan and would be love to have the R2D2 droid version.  Would it be possible to control the original boost set with the new droid specific functionality, or is the move hub not compatible with the Star Wars app functions?

I am thinking of building the R2D2 droid from parts rather than buy the whole set again.
Theoretically possible, but I think you'll find that the droid set contains quite a bit of lego elements that are rather rare, and hence difficult to find in your own collection or from other sources like bricklink.
But at least the electronics can be re-used from the 17101 set.

I myself bought the 75253 boost commander droid set.
You can build all three models, but motors and hub needs to be switched from model to model.
Since I had a couple of 17101 Lego Boost set lying around, I used those components to complete the other two models.
You do need a couple of extra parts, which are a bit easier sourced from your own collection or bricklink: