About 15 years ago, when I worked at a sign company that made gas price changer signs, we used our router to cut vinyl for the numbers. It was an ESAB Signmate 2000 with a 10' x 20' bed, and it was a pain.
Between taping down the material, and making sure that the bit didn't go over the alum we used to keep it flat.
Someone is much better off getting a plotter. Expecially since they are not as expensive as they were.