I got my 660 about 6 weeks ago, and I too am dealing with this hardwired mount problem. Initially, I just used the automotive mount with the suction cup, stuck it to my speedo face, and used the 660 display to read my speed. However, without a cigar lighter on my Deuce, I just used battery power, which is a pitiful 2 to 3 hours max.
I just lifted the tank and ran the hardwire for now, but I told the Garmin guys this was a pretty dumb move. I guess they had a lot of problems with the 550 cradle and this was their fix? Imho, if they had a waterproof 11 circuit connector approx 3" from the cradle, with a quick clamp bar mount, that would be the best of both worlds. For those who want the perminent mount, they could use the included ball mounts, or RAM has 100's of optional mount components.
However, seeing Garmin probably won't consider this at least until the next generation units, what I plan to do is buy a second motorcycle cradle, remove the cable, and just run one end of a SAE cable for the power. Then I'm going to run my battery tender lead, which is now tucked up by the oil bag, and run that up in front of the tank. For the storage, I'll just connect the charger up there. When I'm riding, I'll connect my Zumo to it, only when I need it.
That's about the best 'solution' I've come up with. Thoughts?