Handlebar switches

I have decided to implement a brake light, which I want to trigger using
Hall-effect sensor mounted in the brake lever. Unfortunately I still
have only three wires for two switches and a Hall-effect sensor, so I
would have to change the digital switch readings (on/off) to ADC
readings (voltages selected using voltage split on resistors).

Here is the schematics for the whole handlebar electronics, and the
symbol file and datasheet for the Honeywell SS341RT Hall-effect sensor.