The ADR requires prevention of starting and prevention of moving forward controlled by the one key. The latter can be on steering or gearbox. If its on the gear box it needs to lock in reverse and/or neutral (depending on auto or manual). You are not allowed to be able to remove the key without the lock engaging.
To do this on the gearbox would be very difficult because you need it so the key cannot be removed without putting the car in neutral or reverse.
I think the best way is to come up with a mechanical device linked to the key turning. I can easily adapt a pull solonoid that will pull the pin out when power is applied through the ignition however solonoid malfunction will lead to the wheel locking and that is a risk i cant take. Anything electronic would need some sort of fail safe so you dont find yourself with a locked wheel at 100kph turning a corner on the highway
