If I understand that right--and I'm not certain I am--you are importing the Perl callable functions in one XS module, into the namespace of another XS module?
If so, that's not quite what I'm after--though I understand that my question was unclear.
My thought--albeit perhaps not fully thought through--is to have an XS module that is callable/usable from Perl in the normal way. But to also allow other XS modules to make use of the internal C functions (that sit behind the Perl-callable XS interface), directly at runtime. That is, without #includeing the sources, or linking against the objects or a lib. There would be two or three entrypoints to import at most.
The notion was to remove the compile-time dependancy upon the headers or a lib for potential XS users of the module. They could then decide at runtime whether it is available and use it. Or fallback to other mechanisms. Ie. If the module is installed locally, load it and "obtain the required entrypoints".
Hm. I know I can do this on Windows. LoadModule()/GetProcAddr() are all I need. But I would need a portable solution, and I don't know enough about other platforms to know if there are equivalents.