Never done this before, but I suggest travelling with your bike as luggage to Nice and then drop it off with an air cago freight company near the airport after the race. There are always a handful of these near every airport.

No idea if this one is the "right" one, but just googling I came across it.
https://www.mathezfreight.com/...ervices/air-freight/

There were some people who were in a bind at Lahti this year who couldn't get their bikes on the airplane, so they just shipped them at the airport using one of the freight companies.