I think there is an additional project requirement for tracking simulation data that are not smtk resources, the most obvious being simulation input decks and output datasets. This has been suggested as a “simulation asset” class that is somewhere in the PersistentObject class hierarchy. This was previously discussed in the spring (Proposed Change To PersistentObject), but I dropped that ball.
A simulation asset class would share at least some of the behaviors of persistent objects, in particular (i) ability for projects to use links to assets, and (ii) the ability to use assets in operations, presumably by assigning them to ReferenceItem instances.