+1 Karma to jmizzle for the awesome PvP reward booster pack idea
If Zanz can code it, then I'm in support of it. We could even tie in a few competitions to go with the launch of the system: Design a [Balanced] Booster Pack Expansion (that would be determining the cards that a certain booster can contain and their rarities), Design a Theme Deck (maybe we could make some complete unupgraded decks that could be sold for PvP points), and Random Theme Deck Tournaments (tournament organizers randomly assign a theme deck to each player for the round).
The booster pack sizes should be relatively small (5 cards, maybe?) so that the prices of a pack can be relatively low (obtainable after a few PvP matches). If the booster can be bought after just a few PvP matches, then rares would not be guaranteed in each pack, but if the booster needs a decent number of matches won to get, then having a guaranteed rare would be nice.
Having said that, it would be
a lot of work to code and would also necessitate a tiered PvP system (separated by score), but it would do a lot of good for the future of the game (it would encourage more deck variety in PvP other than control-based Rainbows, for one).