Tuneboy also offers a cruise control kit for the MTS/Diavel. It's around $400, is electronic, and works just like the one on your HD.
The powerlet option is a good one if you must have a cigarette lighter. There are already two power outlets on the bike for heated gear, phone charging, etc. I'm a smoker and can count on one hand the number of times I used the cigarette light on my HD bikes. If I need to smoke I do so when I stop for fuel and take a 15 minute break. Smoking while riding never really worked too well for me.
I know you said previously that you wear a half helmet. I can't imagine riding a bike like the MTS with a half helmet on for a number of reasons...first, I do not think they are as safe as a 3/4, Full Face, or Flip Face. Flip face helmets are the best thing since pajamas with feet in them, especially if you wear glasses. Second, a half helmet allows much too much wind noise to the ears, not to mention bugs/debris to the face. Third, a half helmet would look weird on a Ducati, IMO. Last, a helmet that provides more coverage also allows a more aerodynamic flow of air over the top and sides of the windshield...less buffeting and no feeling like the helmet is being lifted off your head.
Unless you have some particular reason to NOT wear a better, more protective helmet, a Flip Face like the Schuberth C3 Pro, the Nolan N-104, etc allows use of a Bluetooth headset. Both Schuberth and Nolan provide their own versions of headsets designed for their helmets...the Schuberth is one of the most clever designs in that the system replaces the "collar" on the bottom of the helmet, as shown here:
http://www.revzilla.com/motorcycle/schuberth-c3-pro-src-system One other good option is the Shark Evoline 3, which, to my knowledge, is the only helmet that converts to a true 3/4 without removing any parts...simply release the chin bar and flip it all the way back and you have a 3/4. Shark also offers their own version, made to fit, of a Bluetooth. Any of those helmets would solve the third problem...the tunes. Simply load your smartphone with tunes and stream them to the helmet. It will also connect to the GPS system available for the MTS via bluetooth so you get directions in the headset. If you just can't stand anything other than a 1/2 helmet, the same phone could be hardwired via some good earbuds, and kept fully charged via one of the two power outlets on the side of the bike.
Just food for thought...