Hi Dar! I am in WI too. In fact I just picked up the above project in Milwaukee on Monday (drove more than 3 hours round trip LOL).

I wouldn't get the Schwinn if I wanted a true mixte. I'm pretty sure the Schwinn mixtes only have a single wide top tube that splits off at the seatpost.

I don't know the answer to your other question but I'm guessing that it would be complicated but since the shifters probably don't index, perhaps that gives more flexibility.