Some people have a ‘big bag o dice’ which contain all sorts of creatures and oddities. I wouldn’t want to roll from their pile of dice of varied sizes, colors, vintages, makers. In the last 15 years, there have been a profusion of dice that have fancy numbers or just weird symbols, and some people mix all that in to their pile.
I feel like it is easier just to drop the $9 and get a set of Chessex die for every player. I buy them just because I’m out of gaming junk to buy and I want to support the stores we play at. I don’t know if they are concerned about randomness in their production (how could they with that cool swirly plastic?) they look great, and they’re all about the same. There are two sizes of d6, one for Warhammer and the other for RP/Wargaming. Other people want to play with a collection of dice–I want people to use SETS of dice.
I would agree to such a ban, DJ, or a rule that all should bring a similar set. I don’t feel that dice cheating is a big problem in the tournament. My general rule is that with a certain amount of attention and vigilance by all players, most cheating (and slopping, also) can be deterred because it is much much harder to do when you play against people like me, who have extensive experience with cheaters (not in AxA or one venue but over a whole lifetime) and actually watch the other players roll.