So if someone built a bow with a decorative ridge that happened to be located near your thumb, that would be okay?
On a personal level, I have been using a metronome program recently to help me slow down my shot. The program is free, and is an app on the iPhone. You can set the number of seconds, and it will click at the desired interval until you stop it. It plays through my hearing aids, but would also play through an earbud. It doesn’t make any audible sound outside the hearing aid or earbud. It essentially functions like a grip sear, but I don’t have to move any part of my body to use it. I would probably use your feather to nose trigger, but it doesn’t work well as a trigger with a dead release. I haven’t considered using the metronome in a tournament, but I wonder if it would be legal if I did.