1. Titanium Brompton which I would attempt to spread the rear frame to 135mm to accomodate an Alfine 11 (I have already a steel Brompton with Alfine 11 which is fantastic). Ben Cooper has spread a few titanium rear frames in the past so it is possible.
2. Dahon Curve SL or Mu XL with 135mm horizontal dropouts to fit an Alfine 11 and Gates Carbon Drive. I'd prefer the Curve SL but probably would be resigned to the Mu XL because of frame clearance issues with a 70t Gates chainring on a Curve which probably isn't possible.
3. Dahon Helios XX with 130mm ultralight aftermarket Capreo compatible hub and lightweight accessories for a superlight bike with a reasonable gear range.
4. Dahon EEZZ new 3-speed model
5. Detachable Moulton because of the beautiful iconic design (and potential for portability)
But my ultimate bike would be a full titanium or carbon frame Brompton with Capreo compatible hub and enough frame/mudguard clearance to mount 1.50+ tires if necessary.