Bah everyone knows versailles is the best place for the kings to reside.Seconded on the Tulliers. They've been interested in rebuilding that to fix the chink in the Grand Axis and add more space to the Louvre for some time.
Perhaps something like a rebuilding on three floors+ cupolas and attics, with the museum taking the ground floor, the first floor being a mixture of state rooms and museum space (so paintings and items in the context of formal state rooms), the third floor as the private apartments of the family and the attics as extra offices and so forth.