I'd go mixte, upright bars, nice grips, MTB shifting/brake levers.
I'd not go mixte French before a certain year, due to odd parts sizing.
I'd look for Japanese mixte due to interchangeable parts.
I'd run road wheels with as big a tire as you can get.
Be careful, do it right and she'll be fast.

Not the best solution, perhaps, but it's what I'd do.