When creating a new data asset, it is not possible to select a Data Asset C++ Class or Derived Blueprint as its base class.
This did not occur in 4.15.1, this is a regression.
Result: Notice that the C++ class and the blueprint class are not available in the dropdown of classes to derive from.
Expected: The classes created in the repro steps would be available to derive from.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-44389 in the post.