A little more reading leaves me somewhat more confused. Even before the changes I made last night, the Context did not represent a 'cxf-independent' Aegis API. We really don't have one (in the sense of a single class). The comment at the top of Context says that it's per-message, and indeed it stores a collection of attachments.
Let's imagine a new class called AegisContext that works like my previous email: it has a type mapping registry, it manages overrides and configuration behaviors, and an AegisDatabinding uses it. The existing context might get a new name or might or might not lose some functionality to the new class, and the databinding class would go on a diet.
