OK Now If I am thinking out loud here
Firstly you have an electrical fault somewhere and I don't know what wiring you have and who knows what has been changed
Finding that fault I assume you want to get around
Consider this as a first step ( if you are willing to take the risk )
Disconnect the R/W from the solenoid -- cap it so it wont touch the metal or frame
Have a wire from + on battery again not touching any other things
One end on battery.
With the other end you touch the place where the now removed R/W was
Report if the starter spins and even better if the bike starts.
Obviously being careful not getting current into yourself
And after the test remove the wire altogether
Dont do this immediately so others have time to protest ,those with better knowledge about the other features that can prevent startup
and if this is wrong
look at post # 34
If it works a piece of wire with a springed starter button and a fuse can solve it.