Bill, thanks for your assistance. I apologize for the late reply. To
make a long post short, I managed to get things working, at least from
a prototypical standpoint. I seem to recall that the original problem
had to do with unresolved symbols (or, more specifically, a complete
lack of symbols) in the main vxWorks image. Before loading the module,
I manually added to the system symbol table those symbols defined in
the vxWorks image referenced by the loadable module.

We eventually figured out that two discrete interfaces were necessary,
one provided by the vxWorks image for use by the loadable module and
one provided by the loadable module for use by the vxWorks image. Given
our requirement that we support, if not elegantly handle mixed and
matched interfaces, that opened up a whole new set of challenges.

We ultimately chose to use two interface classes, one implemented by
the vxWorks image and one implemented by the loadable module. Although
it sort of looks like COM and quacks like COM, it's far less
generalized. A prototypical version of the code was developed and it
looks like a viable approach.