How about, upon pressing a dedicate genre key, it loads a separate menu, with entries either defined by those in the genre tags of the system xmls, or alternatively from individual genre xml files (e.g. RetroFE\meta\hyperlist\genre\%SYSTEM_NAME%\Strategy.xml).
By doing this we could use the genres already compiled by the expansive hyperlist project.
If a game is listed in a dedicated genre file, that should take priority over the system xml's. If a game is listed in multiple genre xml's, it should be displayed in both genres in the menu
A universal layout for the genre menu could be defined using genreMenu tags in the main layout.xml, and could feature dedicated reloadableVideos,images, logos,etcas the themer desires (could be found in _common\genre_artwork or "collection name"\genre_artwork depending on mode attribute)
Alternatively, each system could have a unique genre menu set up, loaded from layouts\"layout name"\collections\"collection name"\layout\layout.xml or a dedicated genreMenu.xml (i'm not sure which would be better).
Upon loading a genre (e.g. Strategy), it would use the same assets and layout as the current collection (just as if we had loaded a collection from the main menu with all games displayed), the only difference being that all games which do not possess the correct genre are filtered out and not displayed.
Favourites could be displayed in the genre menu as well (perhaps at the top), but, as before, can also be accessed easily through the nextPlaylist control (which seems to only load the favourites playlist and not any genres, maybe it could do with being renamed for clarity, but keeping the old name for legacy purposes) and games can be added with the addPlaylist (addFavourites) control.
Perhaps we could also get a general "favourites" control, which overlays a (customisable) menu over the current view with the option to view favourites or add the selected item to favourites, it would help to make the options more visible and understandable to general users, without having to clutter a theme with many control prompts.
This functionality could also be used to add an optional "exit menu" upon pressing the quit key on the main menu, although I would definitely prioritise the genre features.
Sorry for the long post. I'm not sure if this would fit the needs of all users, and i don't expect anything similar to be coming any time soon. I just wanted to share some ideas and let everyone else discuss what they think should be done.
If you need me to clarify anything, just ask and I'll try to reply explaining myself.