I'd rather it didn't have the dexterity option. I don't think I'd play it if it did unless the reward was better than fg's.
Unless the player is level 80, FGs are mechanically tougher than T500 decks. I think he said that a certain number of consecutive wins would allow for spins with only rare cards on them, as far as rewards go.
Even with level 72 can you build full fledged fg decks as long as it doesn't have more than 36 cards. (75 here, so that makes me smile)
I would indeed hope the rewards to be better than fgs, since players can think up nastier decks than the fgs are. Though on the other hand, crappy decks posted on t500 shouldn't result in free upgrades...
I think it's a bit hard to balance, since there are both players that think up decks that exceed the power of fgs with them and those whose decks are worse.
Then again, a chance for rares might actually be worth it if the rares truly are rare.