If the card game was to a depth of a full featured game (not mini game, tetra master in FFIX was not "full featured" but still fun) then a well thought out and fair system for the shop could work. I'd be concerned that you can win in game content vs other players that would likely require purchases though, if anything is won it shouldn't be a cash shop packed into a cash shop (say vs npc who have a static difficulty that you can reasonably work up to). Also hype and advertisement should let this be known sooner than later and hopefully be something like a game that can be played within ARR and without (being only available in ARR means you pay to pay to play, p2p2p? duh heck? lol).

Going to be something special in the forums.. and just in general if it is a semi featured game with a fully featured cash shop packed twice (pay for content to then use to win content only available to the paid content) exclusively available within the game. xD