Very clever.
It wouldn't work for me though because (1) my MC's are all fitted too close to the cleaning rod to give myself enough room for the string, (2) the deflection from the string pushing the rod out from the natural center of the front pipe might make it too hard to remove, (3) the rod under tension from the front pipe is going to wear the finish off the rod as it wants to move forward under recoil, (4) it doesn't look very HC / PC.
I could see it as a spare rod though, or one you would just use for hunting, since, when hunting you rarely get very many shots, and it cuts down on the "one more thing" to have to bring with you in to the woods.