Lots of mixte ideas to be found here: http://www.bikeforums.net/showthread...ighlight=mixte

Sun CR18 rims are available in 27", nice and shiny.

I built my wife a mixte singlespeed. Rides very nicely.

I think Mixte's look better with commuter bars than drop bars.

You could soak the rims in an oxalic acid solution remove the rust but I am no fan of steel rims and agree that you should get new ones. I'd ditch the turkey levers on the brakes, too.