OK, I know what the rules say about not getting on a leg of a flight, but can someone tell me what the chances are of not screwing up my reservation?

I need to go to The Hague from IND in September. With a Z fare and the 15% discount coupon from the Entertainment Book I can fly in WBC for about $1600 - except I can't fly to AMS and earn the 15%. If I ticket to Brussels and I have no luggage and I go to the Brussels gate in AMS and am polite...will they allow me to NOT get on the BRU connecting flight without trashing my return reservation? Or will I be forced to fly to Brussels and take the train back to The Hague?

The Brussels flight is no more expensive than the AMS one, but it is more messing around. Again, I know the rules but has anyone tried it and lived to tell the tale?

Jack