If your Mrs desires it then it's desirable.

Some folks might think your Campy stuff is overkill for a "girls bike" but if you want to make a hella sweet mixte, that's one way to do it. Couple of issues you need to look out for: most vintage mixtes sold in the US are sized for 27" rims, putting on 700 is no problem, but the current brakes you have may not reach down far enough to work, so you may have to swap in some long reach calipers, if thats not what yours are. Another thing is to check the clamp size on your front derailleur you want to use; it's possible the more modern derailleur clamp is for a larger diameter seat tube than you average old mixte frame. This means you might have to get a different clamp of just shim under the one you have. Most older mixtes will also have 120mm dropout spacing, so you'll need to cold set the rear triangle (or just muscle the rear wheel in) to get the wider modern hub to fit.

For a new mixte frame (in a whole range of sizes, modern hub spacing, sized for 700c wheels), don't forget to check out the Soma Buena Vista.