it's not a horrible idea... on paper. it wasn't even a horrible idea when tsr did it 15 years ago.
remember the original creature cards? they had a picture of the monster on one side (to show the players) and a stat block on the other side (for the dm).
then there was the "deck of" series. the deck of encounters, the deck of magic items, the deck of psionics, etc.
shoot, we even had 3 sets (750 cards each) of "collectible" cards. not really collectible in the end, because you could buy a full factory set in a nice box. and worth nearly nothing now, i just bought the 1991 & 1992 factory sets for a grand total of $35.
the "deck of" series was nice because you could pull out the spells your pc knew and you had a full reference right there, no time wasted paging through the phb. the tsr cards are very handy too. need an npc? pull out a card, here's your npc fully statted out with items. great for on the fly stuff or even as a jumping-off point.
personally, i would embrace revised/updated reprints of the above card sets (complete sets, that is). imagine being able to take a small pack of (refernce) cards to a game rather than hauling around 3 different books. if i could buy a "factory set" of spells, feats, magic items or what-have-you, i would be quite happy. if i had to buy 108 boosters to find a "wish" or "+3 longsword" i wouldn't be buying any.