Let me try and address your concernsOK so:
-No cruise control. Could use a cramp buster probably, but not ideal.
-Engine possibly buzzy (causing numb hands on very long rides).
-Naked bike even with windscreen might be rough at 70-85 MPH highway for many hours at a time.
Can anyone shine some light on my concerns, esp. regarding engine buzz on handlebars/foot pegs, comfort of the seat, wind buffeting at higher speeds, and ergos? Anyone else think the bike could effectively be used to do a week long tour every once in a while?
Other contenders are Ninja 1000 and the Yamaha Tracer 900 GT, but those are much more touring dedicated and wouldn't be much fun outside that role.
Lack of cruise on the Duke I agree is a pain, the new 790 adventure bike does have cruise, The longest rideout I have done is 8 hours only stopping for fuel and a leak.I try and avoid the big open roads when riding he 790 so the lack of cruise put up with. I use my 1290R which does have cruise.
Engine buzzing vibrations, this is the smoothest twin I have ever ridden and I have never experienced any vibration related discomfort on this machine so I would so do not worry.
Riding at 70-85mph, well any naked bike as we know at these speeds for long distances can become tiring with wind blast. their are screens available, but if this is your major again I would say consider the adventure version.
The +20mm ergo seat double the riding hours I can do in comfort, it reduced my knee ache and bum burn significantly. a must for long hours in the saddle