marki,

Yes, exactly, I was thinking of having some kind of config in the webpart.xml set-up file, but I guess, that is not available at this time?

Could you, please, elaborate with more details on the first part of your response? Is it possible to achieve with this mechanism what I originally asked?
Moreover, a web part instance of a different module should show up regardless whether the user is in a 'reader' or 'editor' mode...

Thank you.