I don’t know if this idea is too complex to code for the architecture, but here goes.
I think for the trading system you should be able to select all of the games that you would like to a “want” list. Then you should be able to select all of the games that you like to a “for trade” list.
Then you can run a search and the trade system will identify all of the members that have a game for trade that appears on your want list as long as you have an item for trade that is on their want list. Then you can initiate a conversation or even look over that persons complete want list to see if there’s anything they want that you have..
Example:
Lets say I want Chrono Trigger SNES. I have a whole bunch of $15 - $30 games in my collection like SMB3, Megaman 4, TMNT 3 etc, but only SMB3 is listed in my “for trade” list. I run the search and it matches me with a user who has Chrono Trigger for trade and he wants SMB3, which is on my for trade list.
However, that’s not an even trade. So I go to that users profile and I see that he also has Megaman 4 and TMNT3 on his “want” list. He doesn’t know I have these games because they are not on my “for trade” list, but I decide I’d be willing to offer them up in order to get Chrono Trigger so I initiate a conversation and offer all 3 games for Chrono Trigger.
Thats the idea I had. What do you think, is it possible to code something like that?