I think the issue might be that Boomerang has taken on Vine's role here, and is more suited on the back of close Instagram/Facebook integration, whereas Vine is

I think the issue might be that Boomerang has taken on Vine's role here, and is more suited on the back of close Instagram/Facebook integration, whereas Vine is quite separate from Twitter. Focusing on getting something like this into Twitter itself might be a better bet (though I suspect Facebook has it wrapped up for now).