I know Arca Swiss make a handle for holding big lenses carry-style (because for some reason designers don't make big lens tripod collars like a handle - my Sigma 120-300mm has one like that, but the new version with the USB doesn't have that feature).
Only thought is can the monopod head take the weight of an arm at angle using it like a stick? Might be easier to have it bolt direct to the screwthread for the monopod head rather than onto the head - otherwise neat idea! Hope your toe fixes up soon!