It seems like, for many people, it was hard enough to get the raid loot you want. The new system will make it even harder. I suggest that rather than being assigned an item in the chest, you get a token that can be turned in for a choice of rewards - maybe not a choice of every reward the raid has to offer, but at least a random 4-6 items or so to choose from (with no repeats!!!!).
I haven't run Spawn of Whisperdoom lately, but if I remember right, that's exactly how those collectables work, so the game mechanics are already in place.