I've came up with this idea too, but ran into a problem.
It's not fair to do only some people, or after certain requirements.
It's also not going to work with anyone who signs up gets a card. Maybe, if you make an actual game ( Simple like Pokemon ) and have a leader, the leader would be your card, which only you have, based on your stats. If you donate ( Say, $3.00 ) your card can be put in. I say having everyone would be a problem because the higher ranking cards would be rarer, but you can't have a common card if there were so many of those Bronze ranked ( Assuming they are common ) cards to collect.
If you need help with anything, I can help after winter break is done. (January 5th )
I do have skype, message me and whenever I check PMC again (Away due to break) I'll add you, but won't answer until break is done.
Oh yeah, make sure they have to sign up first! Otherwise illegal alternate accounts or inactive accounts will be rampant. Also, find a coder. It'd be much easier if you had bots scanning registered players for their stats.
Final note: I'M IN!