lcrider

I have a set of Mavic Cosmic Carbone SL wheels that I bought used from a guy who had raced them. They are an older vintage (yellow decals, probably 2004-6). The rear wheel cracked on the rim at one of the nipples and my LBS tells me it is toast. He called Mavic, who said they no longer have those rims or rebuild those wheels and I will have to buy a new rear wheel. I have a few questions:

1. Does anyone rebuild those wheels?
2. If I do decide to replace it, is there any reason why I shouldn't put the newer version of the Cosmic Carbone SL's on the rear and continue running the old version on the front?
3. I really like the aero benefits of the wheel (I live in the Low Country), but if I found a good deal on a different aero wheel, would it be foolish to mix a different brand of rear with the old Cosmic Carbone SL on the front?

I've seen some of my older vintage Cosmic Carbone wheels on Ebay, but I'm reluctant to buy used again since I only got about 2000 miles on the last wheel before the rim cracked.