Although I agree a small solution, it would be starting something and giving commuters/ shoppers an option which they don't currently have.
As a guess (and I am no expert) set up costs would be low as busses run by there already and the car park is built. So just signage/marketing to advise...
I've said it before, build a large car park out of town (or even use Bridge car park weekdays) and have a shuttle bus run into town. Commuters could park all day, visitors could miss the exorbitant charges in NCP etc, shuttle busses direct from the car park to old steine/ Churchill square every...