3rd Concept: General Mode

You can configure a button per mode to open it. Additionally, you can configure buttons to switch between modes in alphabetical order or that show a menu that allows you to choose another mode. As these buttons have to work any time (and not only when a certain mode is active), they are saved in the general Mode.
All other modes per default contain a definition that, when the mode is loaded, additionally loads all definitions from the general mode. The definitions are not copied, but only loaded. They cannot be edited and are unloaded when the mode itself is unloaded, i.e. they only work as long as the mode that loaded it is active.
So, every mode can/should "import" the general mode, however, it does not have to. To import it, create a new definition with "X10Receiver/Definition list loaded" as the event and "X10Receiver/Additionally load definition list" as the only action.
Definitions, that shall always be active (e.g. actions to control the master volume) can be created in the general mode. Please note that it is possible, that one button executes multiple functions, this way (e.g. controls both the Winamp and the master volume). In that case, both functions will be executed (causing the volume to be changed twice as fast).