I want to add a voice of support for this. The business case (or at least the one I'm interested in) would allow people to better tune their tweets to improve social engagement. Right now, if you want to monitor the click through of links, you end up having to insert a link shortener between t.co and your destination (because of the many tweet-to-one page data model you create if you tweet the same link more than once).
But wrapping a link in a shortener potentially obscures the destination and therefore creates friction for the user. A user has every reason to hesitate when they see the URL expanded in the Tweet is bit.ly, or whatever, instead of the ultimate link. And so the overall Twitter experience for users would be improved if we could drop the intermediate shorteners we need to have now to capture statistics.
I hope that helps get this valuable addition to the API prioritized!