As far as the name "Surface" goes, for all those who suggested it, I think changing the model line from Lumia to Surface would be even more confusing. For one, the name Lumia is pretty recognizable when it comes to mobile phones. It's already established, and axing both the name Nokia AND Lumia would anger Nokia fans even more. I think the name Lumia should most certainly stay.
Second of all, the name Surface kind of implies that it's running full Windows (we had this issue before). Keep the Surface line for all Microsoft devices running full Windows, and the Lumia line for all devices running a mobile version. I think that would also help cut down on confusion.