You'd push left and right to flip through choices. Once you pick one, you'd push up or down to enter into it. That stage would be a roller of choices for something like subtitles...
That would be fine for something like subtitles, but not much help for something like descriptive chapter titles. Nor does it provide the means to see all menu items and their current settings at once. To be fair, neither does my description of a 'full menu' mode. I suppose it could be a two-column list of Menu item : Current setting (with items set with sliders shown as values rather than sliders). When a menu item is selected, the column of current values would be replaced with the available values for that item (with the currently set value highlighted). Or should the current values remain, and this pop-out from the position of the selected item? Horizontal sliders could be replaced by vertical sliders...
I hadn't thought of it before, but sliders aren't used for everything they might be used for. That makes sense, as a slider for something like horizontal/vertical position is rather pointless—the screen itself is providing feedback. On the other hand, one for Zoom would have the advantage of being able to show the current setting relative to 'actual' and 'fit to window'. Hmm...Or don't use sliders at all—just show the value. It works, and user's aren't likely to want to change Volume or Play position using this mode.
BTW, since the point of the 'full menu' mode is to display all current settings at once and then all available values for each item, it shouldn't be a timed display. It won't be possible to predict when the user is finished using the menu. <Left> from any menu item would provide a logical exit, and <Escape> would exit the menu from anywhere.
To be clear, I think your idea suggests sensible improvements to the current OSD, it just doesn't replace the need for a 'full menu' mode. The most important aspect of that is displaying everything at once, not how individual settings are changed. It's the sort of thing I would use routinely at the beginning of a movie—just to verify the default settings are suitable. As others have pointed out, it's also much closer to the form of OSD used by entertainment equipment—and therefore more likely to be understood by those not familiar with MC.