I haven't studied the auditing capabilities in detail yet. You guys probably know more than I do.
Ward created the auditing capability in Cabana primarily as a demonstration. I'm not sure he envisioned it's being used as a base framework for other applications.
I agree with Dan that a Cabana module to manage the EntityClass and EntityProperty model objects is in order--a simple SummaryDetail or SearchSummaryDetail page should do the job. That would get you the ability to manually add, delete and edit the metadata for audited entities (assuming they inherit from AuditableEntity).
I could also imagine a view that displays a grid of all entities that inherit from AuditableEntity with check boxes to automatically populate the EntityClass objects. A similar mechanism might be used on each EntityClass object to populate its child EntityProperty objects.
I think I'd prefer this approach rather than doing it directly using TSQL in the database.