I don't think asking your wife to flirt and dress up for you is stupid. Okay, flirting (depending on what you think is flirting) may not happen the way it happens with other people, because like others have said - it's a different person, she doesn't LOVE them, etc. But getting dressed up just for a night out or in with you should be fun and exciting for her too! I LOVE getting dressed up for Keith. It helps that he also tries to do special things for me. There's really no outfit or anything like that, but he will compliment me as much as he would any other women, he quite obviously appreciates it, and he spoils me rotten afterwards for treating him to something special.
I think mixing up what you two do together helps ward of any possibility of jealousy. I personally won't do anything with another man that I wouldn't do for Keith.