If you are keeping the stock left swichpod with the clutch switch, it is not hard to use it with the neutral switch the way other bikes do using one diode. Connect the clutch switch between gound and the solenoid. Connect the neutral switch there as well but via a diode (1N4000 series is fine). There is some risk in allowing starter operation in gear with clutch engaged.
I don't know why they used the complex and more expensive SSM - if there is some obvious reason I missed, let me know.