I've started this post before that Alia5 posted his one. So before sending it i say, yeah, you idea of splitting the screen is fantastic, and really interesting. I see only 2 problems in that. The first is that some voices require space, else you risk to don't understand it. But probably it's not a big deal, because changing some words, decreasing a little bit the font dimension... could work.
The second problem is that this is a "short and middle term" solution. I mean, before or later, the space will end again. with a some kind of pages you can expand it how you want. But this problem too is only ipotetic, and i don't know how many more magic features the magic developers team can invent :DD
Anyway, here is the post i was writing before seeing your post (that i like

))
I understand and agree your point, alfatreze.
But consider that, with the actual features in magic lantern, my proposal of menu will be monotab in the most of cases. It's only about future expandibility. I mean, quite all the things that now can stay in a single tab probably would stay in a single tab in this new interface too. But what about when ml will have dozen of new features? there will become a time where the amount of space will not be enough.
Anyway in these days a though about another idea for having more space (inspired by the menu of my tv :PP). Of course the concept of dividing macrocategories in colors is always valid, if you like it. but in this proposal i didn't done.
I think we could use the upper horizontal menu with the single icons for the macrocategories (like now). And we can add a second menu, but vertical, with the "pages" of the category, like in this image:

A big disadvantage of this way is that you must do one more click every time, and i love the way you can jump thru the features in the actual magic lantern. so i don't know if i like it, probably i prefer the previous proposal.
And i add to that proposal a feature. The user should decide the order of the pages. I mean, i imagine a upper menu longer than the space available, because you must move a lot in horizontal to find for example the "focus" tabs. but maybe i use a lot tha feature and i want to put it in first position. Or for example i use a lot the features in the first page of "movie", but i don't use never the second page, so i can put it at the end of the menu.
In this way every user can have a default order (probably should be useful a "restore to default" button

but can change it for better fitting his use of ml, that is a goal that in part is already well accomplished with the hide feature, i think

)
Last tought about the proposal of the image in this post. For who has 2 wheels on camera, like 60d or upper, the navigation should be very easy and useful, using a wheel for the horizontal upper menu and the other one for the vertical left menu. and the direction keys for moving in the voices of menu. But for who has a canon with only a wheel, the interface navigation become more difficult, because moving thru menu with the arrow keys means 1 more clik for going to select the feature you want, and 1 more click to exit and go in other tab.
what do you think about it?