So uhm...just to be clear you want a second greed button? Because Greed = Want. The options are...you "need the item as an upgrade", or you "want the item but don't need it as an upgrade", or you "don't want the item". Why do we need a fourth button? I think that pretty much covers all the options.
I do like the idea of being able to "downgrade" your roll but I feel that could potentially be abused.
