Well, creating a product that allows to generate as many menu templates as possible? It then depends on what type of product a developer wants to sell. A full API plugin for creating menus and more or just a simple product for creating a given series of templates allowing to replace graphics and texts and adding maybe.
A character selection screen menu after all in every game is a series of tiles with the character picture, rarely animated, the tiles can have different shapes. The product should allow to make the tiles of any given shape or include a wide selection of shapes. Any selected character should appear with a user replaceable animation on screen. The menu should allow two characters for versus mode either against CPU or another user, that would be up to the game developer anyway. Ability to add fancy visual particles based to menu elements would be a nice addition. Transition and ready to replace sounds for anything would be a good thing too.