Purple/black connectors from your pic of your controller must be for motor cut off (high brake). When you push/pull brake handle motor cuts off.
I think this purple wire in your picture is the same purple wire in the diagram I sent. It only has different connectors, but it is meant to cut off motor when brake lever is pulled (high brake).
I doubt that you will be able to connect second throttle for variable regen. Unless there wouod be some knowledgable person who could take apart controller and resolder required wires but than again we don't know if your controller is programmed for second throttle.
Btw if you require Bluetooth module I have few modules for sale. You can program controller from Android phone. I would sell it for ~28quids including shipping.
CN 5.5kw scooter resurrection in progress
E Mindless Maverick Talisman longboard, 2.2KW motor, 150Amps controller (gone)
Scooter:Mach 1600w, (sold)
Bicycle: Giant NRS, 2806, ping 48V 15Ah, stock Infineon, (sold)
Bicycle: Trek 4300, 9C, ping 48V 15Ah, Infineon 25A, ~18Wh/km, max speed 45 km, (sold) [/size]