I love your Will/Morgana theory and want to have it's snarky and argumentative little babies. Will would totally be the kind of guy who, while telling Morgana she's ten kinds of idiot with a side of naivete, would also be opening doors and whatnot for her. The thing where he's an ass but does remarkably polite things out of random habit. And Morgana wouldn't notice any of it because everyone does that for her, but Arthur would, and that's why he doesn't intervene in his brotherly/potential paramour way.