There will be a bare-bones content type in the bootstrap wagn.  The question here is what the minimum that can be.  No, or pass-through formatting where if we are formatting for html, this is like an current 'html' card where no clean_html processing is done.  For XML or really any type by analogy, if it is legal XML going in, we should be legal XML after it is expanded.

It may be two types in expression, one that doesn't do transclusion processing and one that does.  This type may also have a more basic set of view options than is really desirable in most wagns.  A lot will be possible just with Hands of Cards design features, patterns and related DSL cards to extend this basic type with validations and the like.  Some module overloading will be a part of all wagns in the future.