1) The data source designer erroneously presumes that a non-nullable foreign key implies that the associated entity must exist. While it may be reasonable to presume so, the constraint shoudl be editable. Presently, and perhaps because I am new to LightSwitch, I now have to jump through hoops to accommodate this conflation over an existing schema I do not want to modify.
2) Self-referencing relationships of the form Table.ParentID (0..1)->(0..*) Table.Id are not being represented well. In particular, the navigation properties should occur in the "must have" and "can have" descriptive clarifications. Presently, it is unnecessarily obtuse.