-Just an idea:
-Peoples are already finds out what "secret game" is and it is only problem for the ones, that can't find out. So it makes act of hiding the game meaningless.
-So idea is: First; don't hiding the game(For people to not use claimed keys.). Then; without claming the key, using for a better or another game.
Not sure exactly what you mean by "hiding", game=key? If it's the reveal code bit with claiming keys, we need some way to determine whether we have claimed keys or not, else it will be too hard to figure out if we claimed a code or not, which will make it too hard to figure out if a code is for a game we can give away because we already have it. I wish it showed which games have been claimed from the list without having to send a email though.
-İndiegala is already has a way for learning the price of the game on their system("Calculate" button at giveaway creation).I am guessing there is a "tier system" for all the games at İndiegala as it is on the "Gameplay Giveaway Rules".
It checks the base price of the game when not on sale, your reward is based on that alone.
-So persons who win a key can use the keys for buying another or better game.
-For having a "Tier 1(İndie game)" game: Offered game must have a higher price.
-For having a "Tier 2(Popular indie game)" game: Offered game must have two times higher price.
-For having a "Tier 3(Popular games / AAA games)" game: Offered game must have four times higher price.
-Person can add more than one game for the trade.
-For limiting: Only the game that exists more than one on the users existing game list is tradable and one copy must remain.
-İndiegala can limit tradable(Buyable) games by making a list for tradable games and add a rule to system for trade of only those games.
-I think this would be more better for both İndiegala and users. Numbers can change and ı think this way is more profitable for İndiegala and people can use the games that they win second time.
-I would use 4 or more of my games for a AAA game. As AAA games are likely more expensive; ı am expecting to use more than 4.
These keys seem to be bought in bulk. Most keys you win are obscure keys, keys for games that have better more popular versions/more up to date (I imagine sometimes its them giving away keys hoping you'll buy the more popular version) Games they have on sale are different. Your suggestion is way complicated, probably wouldn't work with their business model, there is no point in discussing your suggestion since you can be sure it'll never happen.
I mean they can't even make sure to not give away keys that they already gave away to someone else, or to not give away keys to games with solid negative ratings, or giving keys to games that are already free!