Straight up ask them; why? What is the purpose of this rule you're proposing? Mechanically. If they have a well thought-out legit answer, maybe it's worth considering. If there's stuttering and humming and hawing and equivocating, you smell something fishy, don't waste your time, move on immediately. Tell them straight up; "It's not worth our time to even consider, we'd have to make handouts, alter char-sheets, the other players would have to become familiar with it. Just no. There's nothing wrong as is." For something like the range table, there's nothing wrong with the vanilla table, it's (and this is important for the player to know) just an abstraction of reality meant to employ a game balance thought out by the designers of the game, the only reason to modify it is to shift their designed balance. In what direction(s)? Why? If you haven't found it imbalanced, why consider shifting it at all? It would just make it harder to reference for other players and an inconsistency that could effect presumptions other players have already made.