Here's an idea somebody can make money with if they want to spend the effort:
How about a single, full length (width?) capo with six individual firm rubber "fretting surfaces." The rubber surfaces could be cam/D-shaped, fairly think/round on one side, say maybe 1/4-3/8" thick , then flat and thinner like 1/8" or less on the other 3 sides.
These sleeves would then slide onto a thinner flat metal shaft, like many capos are already constructed.
Once assembled, 6 such sleeves could be turned independentlyso the thick/fretting surface is either facing towards the strings or rotated to the backside. As long as the fretting side is thick enough, that are turned around to the backside would be far enough from the strings that they wouldn't buzz. Now you've got a single capo that you could quickly configure to fret whichever strings you want and leave the rest open.
Anybody feel me on this? you could turn them around like a combination lock.
[EDIT] Well, I'm a little late on the idea, I guess... Started looking around to see if there's a capo that's already built in a way that you could cut it into 6 segments and use it this way. Lo and behold, there's already a capo on the market that is essentially what I'd imagined... Since 1976!
Third Hand Capo
