A lot of people are pairing Brees with Moss. Not saying Brees, in his prime, can't make those deep outside throws to Moss, but if these 4 players were to actually play a game together I consider what is going to be complimentary. Brees hasn't ever been that deep-outside killer where Moss thrived. I like him with a guy that can work more of the field, especially the seem and over the middle. Rice seems like a better fit because of his versatility. Much like what we have in Thomas right now. I'd also consider bigger guys like T.O., Calvin Johnson or Fitzgerald as unstoppable combos with Brees.
For RB, I look at what Brees is able to do in the pocket and his surgical-like execution on play-fakes, hand-offs, footwork etc. So a guy you can work into space and get the ball to consistently would be ideal. Barry Sanders fits the bill perfectly. There's a reason we've always had a shifty back as part of our attack. Its not just because Sean likes to do so much with them, but a bit of it has to be the play-style and execution of Brees.
For TE I look at what Brees was most successful with and that is obviously Graham. So a tall, athletic TE that can work the seem and fight for tightly thrown passes. Tony G and Gates have that build and have had great, long careers, but I think Gronk, at his peak was more dominant than any other TE I've seen. I would say Kittle as the potential to take that mantel like Thomas does over Rice.