Sealing a part of export?  including partial sealing.
Make defgeneric a part of export?  Other type & function signature?

Partial ordering of modules can be used to determine initialization order.

Evaluated specializers, superclasses problematic since this means that
definitions must sometimes happen at a definite time interleaved with init
forms.

Recursive type definitions
Recursive/mutually recursive functions
    A true circularity that must be resolved