I fully support "Ref Ump Welsch's" white hat who hit the nail on the head when he correctly told the coach:
"This is a freaking Saturday morning freshman game, give it a break!"
I believe these situations require a little common sense.
For example: In the (JV or lower) pre-game conference when I ask if he runs anything unusual, the head coach says "No we are still learning to snap the football , but OK Ref, I got a guy that wears #99 and he plays left guard the whole game. I might say Coach do you have 50-79 number he can wear? He usually responds with say "No, he is so fat he can't wear anything but 99, crap ref, we are lucky his uncle Fred is a taylor cause he had to sew two jerseys together just to make one large enough!" Or, he might say, hey ref, are budgets are so tight we are lucky to find enough white jersays to field a team. Either way, you need to take the coach at his word that he is doing the best he can to field a team,
inform the opposing coach of the situation, and kick-off the game on time.
After all;
"This is a freaking Saturday morning freshman game, give it a break!"
Oh, by the way, my usual response is I tell the head coach (of #99) that I intend on informing the opposing coach of the #99 situation AND; unless I return, consider it OK for 99 to play left guard. When I inform him of this, it is not unusual to get a response of something like; Geez ref, thanks for being understanding and working with us, that guy we had last week was a real by the book Bob, he flagged 99 for "Illegal Numbering" and so we were stuck, #99 didn't even get to play after that.
That's my 2 cents