I thought maybe the whole screen would be shrunk and positioned in the left or right corner, kind of like letterboxing but on the top and side.
It's not a horrible idea and it's obviously going to be optional - don't like it don't use it - that's a tough concept for some people to grasp though.
Shrinking the whole screen would sort of defeat the purpose of the larger screen though. I'd prefer to keep a full display screen but have the on screen controls be within one-hand reach. Potentially have them transparent or zip out of the way when you aren't actually controlling anything.