Would you consider allowing a random contest to be performed this way? For example, there will be only one item being shipped chosen from all entrants. If only one person is receiving an item, there is no reason for everyone to send their shipping address, and choosing out of unpublished codes can lead to possible claims of not actually giving anything away.
Sounds like a nice system for the Collectibles section. Would it also be possible to make the giveaway accessible to anyone, limiting the giveaway to the first [insert random amount] people, preferable with a rank above Full Member (or a different prefered rank)?
Those are possible under the current framework. For limited numbers, you can just stop accepting codes after a while. For random winners:
1. Have people send you a Bitcoin address along with their code instead of their mailing address. Also have them save a copy of their code just in case.
2. Every time you receive a code, publish a hash of it.
3. Choose a winner from the public list of hashes using an acceptable method. The winner should contact you with a signed message using the Bitcoin address you negotiated before. As a fallback, they can also just give you their code again, since only they
should have it, though I'd be uneasy using this as the primary method of authentication.
I think that this feature is very niche. Maybe I'm wrong, but I expect to get on average fewer than 1 giveaway-creation request per month. So I don't want to create a big, complicated system for it.