JUST DO IT!!
If you are in for the upgrades- go KL. All fares upgradeable/ Free WC access/ Can upgrade at AMS lounge if seats available/ Cannot downgrade more than one level yearly/ and you will still get the domestic upgrades on NW sometimes even CO. You have nothing to lose except perhaps some of NW miles promotions (MilesaPalooza, etc.).
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KLM PE,HHonors Diamond,SPG Plat,PC Plat,SAS Silver