As a programmer, it could be possible. With Magic Lantern on the sd card, it could go like this:
1. Turn on camera
2. At this point, where ML would normally load, in this theoretical instance it would check to see if SET is being held, if it is, then let it load as usual. If not, then bypass the loading of ML (in other words, run the same script that occurs when you do hold SET upon load)
1. Turn on camera
2. At this point, where ML would normally load, in this theoretical instance it would check to see if SET is being held, if it is, then let it load as usual. If not, then bypass the loading of ML (in other words, run the same script that occurs when you do hold SET upon load)