I love the idea of boosters, that's one thing I miss the most about CCGs. I don't have a lot of time to play PvP, though, only maybe a few minutes here and there. Most of my games are spent playing a few turns and then leaving the comp for a while to come back and finish the game later.
I am in favor of spending electrum for boosters, say 300-400e for a booster of 5 cards, with the chance of 1 rare? 700 for 10 cards with the chance of 2 rares?
Then you could still have the bazaar, just increase the cost of each card to offset for the inclusion of boosters (we want to reward people for wanting boosters, not for purchasing singles, right?)
I also would like to propose some sort of advertising bonus if possible - click on a banner, get 50e off a pack of boosters, once a day...