I quite agree that the passage from which the name “Lucifer” is taken has nothing to do with the devil but is about a human king. But a name is just a name and its only function is to label so you can talk about it, and in this case Lucifer is the label for the angel before he became the adversary. And yes, as indicated in Revelation 12, I think the snake in the garden was an arch-angel, leader of a third of the angels in heaven. And I think he was just doing his job to create challenges for living things so that they would learn and grow. But as necessary as challenges are, sometimes those challenged fail, and then nobody looks very kindly upon the source of the challenge. Thus we have the snake named “adversary” (Satan) in the Garden of Eden.
I think he is portrayed with goat-like features because he is ultimately a scapegoat – assigned to this role of personification of evil to make it easier for us to choose between good and evil. But I think the angels are more in the nature of tools, like a computer AIs, than persons with authentic free will – a product of design that will never be more than what God made them to be. So I don’t believe there is any reason for sympathy or concern regarding this thing being destroyed in the end. Or is it murder to dispose of an old computer?