My offer stands if anybody thinks they can rehabilitate Smellycat...
I see no reason why one couldn't build a cat proof fence, buy a cheap harness and leash and take the cat walking or hiking, spend more time training the cat, use an invisible fence, take the cat on trips in the car or a carry bag, build a cat enclosure, use a tie out, or otherwise engage the cat in physical and mental activities... might need to go about it a bit differently than you would with a dog - but cats are intelligent and I don't doubt it's doable.