Which parts have no-friction Technic axle holes?
One possibility is the Technic, Gear 8 Tooth without Friction. It was specificially designed to allow axles to slide through it. It can be held by 4 other 8-tooth gears, one of which could allow for the mechanical connection:

 o 
o+* 
 o

+ This is the frictionless 8-tooth gear your axle can be inserted into
* This gear is used to transmit the torque via another, fixed axle
o These are gears pinned to the frame but connected only to the central one


The above solution does violate the 2 studs width requirement, but it still might be possible to use the gear with the fixed axle inserted by half a stud and the removable axle occupying the remaining half stud. This would require a way to fix the gear in place, since both axles would have the same amount of clutch, and depending on your definition of "moderate torque", the interface along the half stud length of gear and axle might prove insufficient.