Enhancement
Currently, an object can only be displayed in the form in the instance editor if the type defines a default view (as a dialog). Instead, the instance editor should provide a generic form view as a dialog for all types, which shows the instance in its default form view. The default form view is the form defined on the type (or one of its super-types).
Test
Display instances of a type without default view in the instance editor and open the form view there.