Having done some research. It looks like a standard 10 speed crankset will work with the 11 speed drivechain. It appears the difference in the 11 speed chain is mostly external thickness, so that the cassette can have closer spockets.
In which case a Rotor 3D, seems a good choice. As they do a wide range of lengths. So maybe option 2 or 3 afterall.
Having done some research. It looks like a standard 10 speed crankset will work with the 11 speed drivechain. It appears the difference in the 11 speed chain is mostly external thickness, so that the cassette can have closer spockets.
In which case a Rotor 3D, seems a good choice. As they do a wide range of lengths. So maybe option 2 or 3 afterall.