That's what the recycler is for... and the various other ways to get enough gran to play the lottery, like ranking and Mirage Master. The GM trading system in Japan is not standard card for standard card, but only for prize or "point" cards. These cards don't do anything in the game, but they are given to users who make certain rankings, place in the top 50 in a free tournament, given out in the FM lottery, those kinds of things. Then you could trade them to the GM's for cards of your choice, for example, 2 point cards might let you chose any rarity 3 card, and 6 point cards might let you chose any rarity 4 card. Generally it would be problematic to let people trade in normal cards because then they won't use the recycler (and manually trading out cards is a lot of work for GM's).
One thing the Japanese do differently, is that since they had a lot more cards then we did when they put in the lottery, they made the lottery only 10 Gran. The chances of getting a high rarity card is very low, however. If we did that, then the lottery would just keep turning up the same rarity one and two cards over and over again which would be very frustrating. Instead, we made our lottery 30 Gran, 1/5th the cost of a 5 card pack, and made the chance of getting good cards about the same as a 5 card pack. This way it's fair, but it makes it hard for people who just want to get new low rarity cards.
But don't worry, once we have enough cards to have the random % work out better, we'll switch to the Japanese 10 Gran system. That means that by recycling 2 rarity 1 cards you'll get enough to play the lottery, which will give you a new low-rarity card. Then, if you don't like it, you can recycle and try again. If you get a rarity 2 card on the deal, it won't cost you anything to play again (since it recycles for 10). The Japanese tell us with this system any player can amass all the low rarity cards in just a few weeks of Mirage Master and ranking Gran.
"Scissors are overpowered. Rock is fine." -Paper