As much as I would probably enjoy the hell out of an allmap format, I find it hard to properly define how it would stand on BotB.
The allgear and visuall formats are easily defined and consumed - allgear is an audio work that you can listen to, and visuall is a visual/graphical work that you can look at. Also, allgear is either mp3 or can be represented in mp3 form, as is visuall with jpg/gif/png. Map formats don't really fit the same generalist format framework. Sure, you could maybe boil it down to "some sort of work you can play/interact in", but it feels too vague and abstract, and also there isn't really a good canonical representation for a map. The closest thing to it is screenshots or gameplay videos, but those can't really fully convey the proper experience of playing the map.
Another way I'd frame it is that while there are many ways you can create an allgear entry, they all boil down to something you listen to. Or even in the case of vgm, there are many ways to create a .vgm but they all follow a well defined spec. The argument for different map types boiling down to something you load into a game/engine and play can be made, but I find it to be a stretch. There's also a lot less common ground across different map/game types.