@jdick this ticket (making startDate nullable) is already being worked on: https://issues.openmrs.org/browse/TRUNK-5331
The other thread, that involves some REST changes, has not resulted in a ticket yet. I asked you a question over there, to help get to a ticket.
On this tangent, Bahmni is also thinking about a My Favorite Patients feature. These would be limited to the user, but it could be nice to build this on top of something that can be expanded to shared Patient Lists.
I’m not sure if we’d want this in openmrs-core, or a shared module, but if you propose a design forum to discuss this then I would be happy to join.