Well there is a way to keep the booking in order although skipping the first leg for a fee - at least for paid tickets.
it's a bit complicated, but it works - a very competent service agent in the KLM lounge in AMS told me that.
Check the Terms/Conditions of AF/KL - 3.4 Flight Coupon Order of Use
(b) Except in case of Force Majeure, any non-compliant use by the Passenger (for example, if the Passenger does not use the first Coupon or if the Coupons are not used in the order in which they were issued) will result in the payment of an extra fixed-rate fee at the check-in moment for the following Coupon (from 30 hours before the departure) at the call center, at a City Ticket Office or at the airport amounting: - for flights in Europe (including Metropolitan France and Corsica) to € 125 in Economy and €300 in Business; - for intercontinental flights to € 500 in Economy and Premium Economy and € 1.500 in Business and La Première (or the equivalent in the local Currency).
(c) The extra fee will not be applicable when the Passenger has used a new Ticket on the same route within 24 hours following the departure of the flight corresponding to the unused Coupon.