Look at it this way. Let's say you have a major fantasy involving your wife doing something, but that "something" is repulsive to her. For example, maybe you have a friend that she absolutely hates. She won't even be in the same room with him. He's ugly, morbidly obese, obnoxious, and always rude and condescending to her. She wouldn't throw water on him if he was on fire. For some weird reason you have a major fantasy of her blowing him - and you tell her about your fantasy. She finally agrees to do it while you watch just because she loves you and doesn't want to deny you the pleasure of fulfilling a major fantasy. Imagine how incredible that would be for you. Now just reverse the roles. Wouldn't you want her to have that same kind of pleasure? I can't think of anything sexual (other than actual physical pain or injury) that I wouldn't do if it meant pleasing my wife. Even if I found it repulsive, I'd just man up and do it for her pleasure.