I think this should be fixed from a different perspective.
How about a manufacturer offering some inexpensive/free software that would talk to your ECU thru a USB port or bluetooth, so the average shade-tree 'tuner' could tinker with settings in a safe manner. Maybe incorporate more 'tuning' features into the infotainment screen? Maybe you could choose a general state of tune (comfy, sporty, racecar, eco), or drill down to specific items.
Maybe you could download the latest 'tune' from the manufacturer and flash your ECU, like you can do with new TV's and almost every other consumer electronic product (without spending $100's at the dealer).
Win-win: people get to tinker, and the manufacturer could design the software/firmware so that any tinkering would be in a safe range (not allowing the machine to damage itself or hurt anyone).
Hackers will always hack. Why not give the 99.9% of people who are not hackers the opportunity to tune and adjust to their heart's desire, safely and with the blessing of the manufacturer.