that could be a... quick solution ?

Honestly I'd point out to the right fix: Cylinder key or ign switch. Maybe in fact the deal is so easy than just the key cylinder ( tipically ).

Will need to remove the steering wheel and middle column collar ( turning switch is enough to get it pulled and hanging out ). Then cylinder key is really EASY to remove. Then you can check the ign switch by itself being free to move to the step back on switch. If works, then cylinder key is the culprit and you will have it hands to fix or replace. If not, you are in the middle of the way to replace the switch