Yes @roman_r_m , I also think so that there is no need for DOI. Citation key is enough to represent a source in the markdown and then using it we can cite the source in any desired format in the final formatted view. As such user only need final pdf with all citation done. There is also another problem with DOI like for books as a source there is ISBN-A derived from ISBN and it not sure it will be available for all books.
So as in the BibTex plugin, we have to work with the local bib file rather than importing it will be good to just read the file , in this way no need to watch for files(kind of like passing by reference).Is this approach is good.