something to consider if you have run out of other mods. The post 2013 commodore uses an electronic cable actuated hand brake. The article is a basic explanation and the ebay link is all the parts you need (save for a custom cable end to suit the hand brake and the handbrake button location in the cabin). It came to my attention from a mate that is converting a Military Dodge weapons carrier and has a similar problem to defender owners that the HB occupies valuable real estate.

Electronic Parking Brakes

VF WN Electric Hand Brake Assembly Holden Commodore Caprice Calais 92277371 | eBay