I’m don’t have ETOPS experience so bear with me, but it would seem to me that the problem with having ETOPS painted on (EG, the nose wheel door) is that it’s still there if the aircraft becomes temporarily non-ETOPS compliant. Every airliner I’ve flown has had a coloured tag in the Captains eye-line stating CAT 1/2/3 etc so you have no excuse, even if you’ve missed the info in the Tech log, to attempt at CAT 2 or 3 approach in an aircraft that’s not capable. Surely an ETOPS / NON-ETOPS tag next to it would be the simplest and more or less fool proof solution?