Yes, something along the lines of your Miyata would be nice. What model is that, and do you know the year? I didn't know Miyata made a triple butted mixte...a pleasant surprise.
Are the Peugeots U08s, PX10s, or something else? Do you like them?
I've always liked the looks of the Peugeots, but am a little concerned about the availability of french threaded versions of the bottom brackets I like. I'd want to put a Sugino XD triple on for her if I could.
I don't know the model of the Miyata but the components I looked at dated to 1986 from memory. Miyata, as you probably know Miyata pulled their own tubing and made some of the first triple butted tubing, or so I read. This frame is much lighter than the Bridgestones mixte I have that is suposed to be 4130.
I have a late 70's UO18 (UO8 mixte) and a late 80's that is internally lugged and alloy wheels and crank. Both have dropped bars and stem mounted shifters.
I know Harris stopped selling the universal bottom brackets but I know a couple of people who installed them without camfering and recommend them. At $17 it is a pretty reasonable solution.