Man, the idea that something could be even, somewhat, maybe, possibly, remotely related to multiplayer of any sort, and some people go completely nuts. I wonder if some even read the entire opening post.
Anyways, it would be nice if you got some cosmetic items for completing Bethesda's challenge of the week/month. It would be near to unlock different variants of the same armor, like a more regal steel design or a darker leather design, for doing certain activities and unlocking achievements. However I don't see Bethesda doing this, seems like it would take time out of production on other projects. I don't think I'd even use it honestly, whenever I played GTA4 I try to skip the Social Club stuff as quickly as possible; I'd hate to give the TES Social Club (Or Mead Hall) the same treatment, THEN have everyone else give it the same treatment and then we are stuck with this feature that noone really uses that could have been used for something else that people would have used.
I like the idea, but if Bethesda already has a complete list of what is going to be worked on/implemented, I'd rather they focus on what they think should go in.