Overall, I like it. I foresee some issues with the responsive matchmaking and timeouts, but it probably won't be a huge problem.
We are going to need some sort of indicator in the marketplace letting buyers know how much cooldown that card has remaining.
@nealmcspadden any cards for sale on the market that are not able to be played immediately will have a small timer icon shown next to the price. If you hover over the icon it will tell you how much time is left before it can be played. I am also working with peakmonsters to add this in to their site soon as well.
A fantastic UIUX idea if you ask me!