It would be cool to be able to make big SuperCharger games, but they would no longer be compatible with the SuperCharger.
SuperCharger BASIC already allows you to create oversized SuperCharger games by recompiling them as CBS RAM games.
SuperCharger Space Invaders only runs as a CBS RAM game after beta 4 grew too large to fit in the SuperChargers 6K:
Other than providing a little extra room for code the CBS RAM based Flashback BASIC and SuperCharger BASIC are nearly 100% cross compatible. A 512K version of SuperCharger BASIC would of course cease to be compatible with CBS RAM games any larger than 10.5K unless the associated CBS RAM bank switching scheme could also be expanded.
Expanding the virtual cart size could probably be supported by Melody boards and the Harmony, but expanding the virtual tape load size would be tight because the firmware only has 8K to work with and can't use all of it though I bet the Encore could do it.
The new UnoCart may also be able to support expanding both protocols.