I like the idea of Adar being an orc. I thought a couple things about his conversation with Galadriel were interesting. The first is when Adar asserts the personhood of orcs, Galadriel's response is to advocate for their genocide. This is not a good look for her, but it puts a twist on the paradox of tolerance by raising the question: what right does a "People of Hate", intolerant in its essence, have to exist?
The second is that Adar implies he believes in "The One", Eru Ilúvatar, which seems distinctly non-orcish. One of the defining characteristics of an orc is worship of the Dark Lord as God. We can see this in Sauron's promotion of his worship among his followers in the Third Age in the guise of Morgoth, with the attendant doctrine that Morgoth is the one true god. Adar's followers, likewise, seem to worship him, and his name/title, "Father", seems to appropriate Eru's title, "All-father". This highlights the inherently hypocritical position of one who aspires, as Adar, to become a dark lord.