Elaborating a bit on the gem system in Street Fighter X Tekken, Capcom special adviser, Seth Killian, spoke about some of the ins an outs on this controversial feature with Gamasutra.
Killian mentions that gems will be balanced against each other, and just because someone buys the special edition, they will not have an advantage over other players. Also, he adds that it's possible not to select any gems before a match, but there isn't a no gems option which locks them out of play.
This is a really good write up if you're interested in more details about the gem system. Here's a snip.
The Money Specter
How players will be able to get gems has also been a major topic of player discussion, with rumors suggesting microtransactions or grinding will be necessary.
"At this point we're still sort of figuring that stuff out," says Killian. "The game comes with some gems, some of them will be available as preorder bonuses and things like that." Some may be available packaged with DLC, as well.
"There's also worry about this guy [that] has more money and buys the special edition -- will he have an advantage over me?" The answer, says Killian, is no. "The gems, in the way we've approached them, are balanced against each other."
"If one gem has a bigger damage bonus, it has harder activation conditions."
Es posible que la situacion sobre las gemas se arreglen... Almenos estan dudando en poner una option de quitarlas, ojala no sea un cubo!