I am currently designing a product which has an lcd screen and three physical buttons that allow for navigation: left, right and select. Currently, this lcd is VERY small so I have limited screen space to work with. Given the menu options, currently the navigation allows you to select from a list of options at the bottom of the screen. I am wondering about the implications of using the left/right buttons to implement more menu features, like going up/down (image on the right). As you can see, when you select the left arrow it can go up to select an upper button. Are there any downsides/user errors that can occur from this design? The main one I can think of is that users may get lost navigating since they may be unclear about when the selector goes up/down vs left/right. Is there any other way to implement these buttons for navigation purposes?
Edit: Additional question, if the user is on the far right button and hits the "right" button, what should the user expect to happen?