Someone probably changed the alternator and then had to stack the wires onto one post for the internal regulator to function correctly.
I'm concerned about your hot wire issue. If you had a very run down battery the wire could get warm indeed if the full output of the alternator was coursing through the wires.
I really like the suggestion of a mechanical switch. This solves a lot of problems but you have to be diligent and not run the engine battery down accidently. The switch is a very simple and fool proof device. No messing about with solenoids and such.
