Illegal substitution question

[ploeger76]

I thought the goal of football was to score more points than your opponent while abiding by the rules of the game. I still think the “at or immediately before the snap” language in the rules leaves an opportunity for this to be a legal technique if timed properly. So it would come down to the interpretation of the rule by the officials. I can’t see where a 5 to 10 second passage of time could be considered “at or immediately before the snap”.