I think generally, European airlines have stayed clear of aggressive belly branding. It’s a bit like make up, what feels normal in some parts of the world can feel a bit too much in others and vice versa. As you say, VS might be the exception here, but. Well…

I can see how some at Ba might love the free advertising potential and maybe they will. I certainly can’t see the point of « subtle » if that’s the case so I suggest « Speedbird » is a complete non starter, if the brand it will likely be either « British » or « British Airways ».

personally as someone who likes the cat and mouse game I f identifying plane types and airlines from a distance and like this to be minimally challenging, I hope they won’t but that’s admittedly a very selfish reason!