Yes! I'm all for this! An Iron Fist and Dr. Strange short could work perfectly. I think that we shouldn't see their origins but rather who they are what they're about.
I thought up this short in my head for Iron Fist:
The camera zooms in slowly and we see a figure standing on a rooftop, with his mask and sash blowing in the wind. A voice speaks, "My name is Danny Rand. I am the Iron Fist." Then we see an image like this:
A brief and quick scene of Danny getting the scar of Shou-Lao the Undying dragon and the Iron Fist power.
Back at Rand Corp., Steel Serpent and Hydra:
2 or 3 minutes of Danny fighting Hydra, really show alot of fight sequences of Danny taking them out one by one with the iron fist.
Then to end it:
Kevin Feige stated he likes what Ed Brubaker and Matt Fraction have done with Iron Fist and Iron Fist's mythology, so having Iron Fist as legacy hero would be the way to go.