Iraty / Parquetout - steep climbs both ~ 6-7km with plenty over 10-12%, iraty is compatible as a stage finish although I'm not sure if they can do it logistically while Parquetout could easily be introduced before a finish in La Mure.
Few days ago there was an interview with Thierry Gouvenou in a french newspaper about Iraty and other basque climbs.
"Iraty, it is far from everything. Globally, this zone of the Basque Country is far from the sites of arrival that we found for the moment. You have to be able to access the hotels. If we have to take a two-hour or two-and-a-half hour bus ride, it's not possible." "We'll get there one day, but it'll be much easier if it's just a pass" "There are often great climbs in the area, but also extremely fast and narrow, hyperdangerous descents."
Better start building hotels nearby.