While you're looking for this feature in the meantime, ping the Bing team and ask for it as an added function of their API. Microsoft is a lot more open to feedback these days.
For feature requests, it would be awesome if you posted them to: https://cognitive.uservoice.com/ (I'm also forwarding your post to Bing).
If you want to get in touch with the team directly about a question/issue, the "Contact Us" widget at the bottom of the Cognitive Services page is the way to go: https://www.microsoft.com/cognitive-services
http://www.bing.com/partners list all the services/APIs/partnership opportunities Bing offers.