I sure that you could fit a brake light switch inside on the pedal rod , under the carpet,
a little VT commodore switch on a small bit of angle mounted on floor . and a small plate on the rod for the button to stop on ,when you push the brakes the rod and plate would move forward making the brake light switch button pop out making the brake lights come on.
I did a similar set up on my Kombi
the cruise control switch works 2 ways
http://www.ebay.com.au/itm/BRAKE-STOP-LAMP-LIGHT-SWITCH-SUIT-HOLDEN-COMMODORE-VY-VZ-WITH-CRUISE-CONTROL-x1-/121452566378
http://www.ebay.com.au/itm/Genuine-Holden-New-Brake-Light-Switch-to-suit-VR-VS-VT-VX-VY-Commodore-/150890560057
there are smaller switches, you could even mount it on the floor in front of the pedals with the button pushing on the end of the rod using that .