Discussed with a group what they have done in the area of end-user-facing UI. Nearly universal response was that they throw away the OOTB UI and write their own. They did admit that they used the OOTB UI as a reference. Also universally agreed that a rich, detailed and interactive REST API document would be very valuable for their custom UI-writing efforts. On the topic of a JavaScript SDK, resounding enthusiasm for the idea, even given the assumption of a rich API doc also available. Consensus was that such an SDK would be very valuable for getting up and running quickly.
Q: Which environments are people using as a REST consumer?
A: With one exception (PHP), all are using SPA JS environments to work with our REST API.
Q: Which SPA frameworks are being used for your custom UIs?
A: React and Angular.
Q: Would you be happy with an JS SDK which is framework agnostic and does not attempt to directly interact with the DOM?
A: Yes, very happy.