Twitch Drops are a great idea for this game and should continue. However, I am not so sure on the streamer exclusive drops.
The reason is that when you have a streamer exclusive drop, and that streamer rarely plays the game, it is a bit frustrating for the players who either really want that specific drop, or the goofy ones like me who are a bit "completionism" and want to earn all the drops.
Exclusive drops within a group of streamers that you are also doing now is great; wherein five or six streamers have the same "exclusive" drops and a different group have something else. But having exclusive drops for one streamer is not fun when it is impossible to ever see that streamer playing Marauders.
Clearly I have one specific streamer and exclusive drop in mind, but I don't think I have to mention names.