I'd like to suggest that the OSD in big screen mode in Theater view also use a roller type interface. I was trying to explain to my brother how to scroll through the options (up/down) and then change them (left /right), and then thought "why should I need to?".
How about if the current option were it's current size, but above and below it were the previous and next options, half sized, and greyed out. Then we would know instictively that up/down changes the option. Pressing up/down would roll the options like the new rollers do in Obsidian theme for navigation.
And how about if at the left and right edge of the current option there were little left/right arrows to show us that the option could be changed.
Finally, all the options allow the user to scroll using left/right through the various choices, except subtitles. For subtitles we have to use up/down to go through the list, and then use left/right to "select" it. Could this be changed? It would be nice if the experience were more consistent.