There are just as many ways to cheat with dice as there are ways to cheat with cards. There is no perfect way to stop this, but warmachine does not hand out dice before their tournies, nor does any other game. If a player suspects another of cheating in any other game, an offical is called over and they check the dice. Same could be done ith cards. If I am replacing any cards the onus is upon me to have my deck correct, if I mess that up at gen con, bad on me....and depending on the offical/opponent maybe DQ'ed. In that case you have to take personal responsibility for yourself and your deck.
Having a new deck for a tournament does not mean you cannot cheat with it. The only way to make sure that every deck is perfect is to hand out decks before the first game, then collect each deck after the game, AND have an officials check every deck before the next game. Repeat till the tourny ends. That will not happen.
What I expect to happen is your opponent can check your cards before the game. If at any point, someone questions your deck an official will come over and check it themselves. Samething that happens in dice games. So adding a suit or 4 does not add any problems in a tourny IMHO