I'm not sure about anyone else but I find that I like to keep my exotic one on for each faction on each of my characters.
What I would like is for them to have the ability to swap over Vanguard rep and Crucible plus being able to keep the rep for the faction.
Just so I the don't need to swap it other with a legendary, when I do a strike or fancy some crucible.
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You can't have your cake and eat it too.