> … there should just be one full time engineer on it …

Agree with everything you just said, except, please make it two engineers. Speaking as a prototypical eng manager who typically inherits these types of projects when "that one engineer" leaves the company, I strongly believe that any job worth doing is worth doing by more than one person. (Plus, a good peer, just to bounce ideas off of and do informed code reviews with, is worth their weight in stars.)

PS: I thought @jack was going to open the third-party ecosystem back up again. That also has the potential to help address this problem. Did that not happen?

[1] http://www.theverge.com/2015/10/21/9586084/jack-dorsey-twitt...