Good idea,I’ve done that on a van door,but my immediate question is extracting the switch from the casting.Take all tumblers out - and just leave the first one in - to hold key in.
...without tumblers and springs flying out?
I can't find a link for the place I bought mine from, but it's one like this:
View attachment 445818
At first glace I thought it was a horrible cheap bit of tat that was going to be useless, but it had the broken key from deep inside an ignition barrel in a matter of seconds! Honestly it was no more difficult than picking up a M8 bolt with a pair of long nose pliers! Just do a Google search for 'broken key pliers' and you'll get plenty of hits.
Alternatively if you're in my neck of the woods (Rochester, Kent) you're welcome to use mine!
I have a few ground up hacksaw blades too. I never got very far with them either!View attachment 445847
They better looking than the set of ground up hacksaw blades I use for the job