Wow. Just wow. Incredibly well done!! You should try brokering a deal between Bioware/EA and Hasbro to mass produce this; then we can all buy one. Just be sure to get your percentage from every sale! Very nicely done.
This is really cool! As a die-hard ME fan, I'd love to make one myself. If you feel talkative, please send me a message or something: I'd really like to know how you made this - especially the cards and pieces.
I can answer any questions you might have, the process goes much smoother if you set everything up with templates, I was using the business card kits from office stores but ended up printing them at fed-ex office and cutting them myself with some practice you can get some very even cards, but to start the clean edge business cards work fine.
As for the helmets I sculpted them from sculpty in layers and boiled it between to "set" everything, then baked the whole thing and cast and molded them.
having a prop-making background helps a lot with a project like this since there are a lot of different disciplines you need to be skilled in.
I may post some "making of" pictures in the near future, since I still have to make one for myself.