PeterPoddy has just mentioned my suggestion: Kawasaki Versys. A 650cc parallel twin. More grunt than an er6, 50+mpg, 220 miles between fuel ups, a small fairing and a fun bike that’s reasonably comfortable.
One more suggestion. What about on of the 3 wheelers from Piagio or Peugeot? Maybe not the image you want, but you get 400cc, good weather protection, and what I would guess would be pretty good handling with twice the grip up front of a conventional motorbike