I view this as similar to the functionality of embedding a SAGE cell inside a WeBWorK problem. We just want to embed the whole WeBWorK problem instead. There could be a login possibility with each problem. I think this type of use could make WeBWorK much more attractive to teachers and make WeBWorK a better teaching tool that can be used in a wide variety of contexts.
It would be a powerful feature to be able to embed WeBWorK problems in external applications. For example, versal allows you to create lesson plans for a flipped class through a drag-and-drop interface, and Ximera lets you do something similar only coding in LaTeX, but both are lacking the ability to ask some useful problem types. If we could embed a WeBWorK problem into these lessons it would make both programs much more useful.