If Jax can't use Disguise Self to hide his wings, then that completely destroys his entire concept as a character. He's supposed to be an infiltrator. Disguise Self can make you short, tall, fat or thin, alter everything you're wearing, including weapons. I don't see why it couldn't turn a pare of wings into, say, a cape.
As for having to cast it over and over, sure. But it just takes an action to cast. That's less than 6 seconds. It shouldn't be too difficult to do, and out of combat, it would be something he would recast anytime people aren't looking. Unless we're going to play out of combat hour by hour, it shouldn't be a problem. In combat or dungeons, sure. Going to the inn, not so much. After all, what's the point of having Disguise Self at will if you can't use it?
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