The few problems and some have been stated. Tap on the shoulder to start could work. Problem comes if/when you are unsafe in gun handling or breaking the 180 rule or some other reason shooting needs to stop immediately. These situations in my opinion are critical and hearing is a must. My concern is in the above situation touching the shooter could possibly have the shooter trying to turn around after being touched with a loaded firearm. Next concern is how will the safety office know when you are done shooting and give the command to remove magazine/empty cylinder show clear, slide forward/cylinder closed, hammer down and holster. How about the starting commands?
I could be wrong here. Maybe there are some match directors out here that could chime in.
You could attend a match with some one that can translate for you assuming you are fluent in sign language and get their thoughts.
You can also contact IDPA, USPSA headquarters and get their take on this.
NRA Life Member, NRA Range Safety Officer, IDPA Safety Officer, USPSA NROI Range Officer
As you are, I once was, As I am, You will be.