Here are some of my opinions:

1) The slant: I don't think that a matrix is a good idea. The wrists shouldn't have to twist to type and unless the parts of the matrix are mounted on separate boards with spacing and an angle between them that's what will happen with a matrix design. The row stagger of normal keyboards is okay as it is for the right hand, but it should've been reversed for the left hand! The "Angle" ergo mods remedy this somewhat.

2) The VK_102 aka "LSGT" key: This key is somewhat of a favourite of mine, as it enables the Angle mod! With that, the distance to Shift is back where it was. Interestingly however, the distance to the right Shift on a non-Wide-modded keyboard is the same as that to the left Shift on a non-Angle-modded ISO keyboard and nobody seem to complain about the former!

2b) The number symbols: I and others have actually made a currency dead key. AltGr+4 lets me type ¥, £, ₤ ₢ ₰ etc as needed. Nifty. For the most-used symbol it can go on Shift+AltGr+4 (in my case, that's £ since I already have $ on Shift+4).

3) Thumbs: Yes, indeed. There should've been *at least* two thumb buttons on every keyboard. Apart from ergonomic alternatives like the wonderful Kinesis, one could use a Japanese keyboard that has a little extra hardware in that area – but at the cost of interesting hiragana on your key caps and the task of implementing the software to use those buttons. Me, I use the Space as an Enter key with Caps (Extend mode). I use that quite a lot, more than the physical Enter key these days.

4) Extra keys: Quite. With the Extend mappings, I never venture out to that area of the keyboard at all. A "Tenkeyless" compact hacker's keyboard is a nice thing.

5) I want the NumPad to be on the home position too, with a modifier key that can both lock and switch to it (like Caps vs Shift). Makes it much more useful and compact. I have that on my Linux/XKB mappings, but so far haven't made a dedicated modifier to go with it.

Just to be clear, I'm not opposed to having a curved, angled or split keyboards so that the columns line up with the arm-wrist axis. But having each row of keys slightly offset as per current keyboards only increases the distance between keys, for no benefit.

The alignment issue is partially dealt with even in mainsteam keyboards, for example this and
this. But the probem is, because all the keys still slant right, the problem is not really solved properly.

There are better designs than mine out there no doubt. I especially like the look of the Ergodox, with its enhanced thumb usage. My post was really borne of frustration at the lack of attempt in mainstream keyboards to solve these design problems, despite the millions of hours people rack up using keyboards every day. Can you imagine any other common workplace tool remaining as inefficient for so long?

People don't tend to go for radical changes, so I always think it's better to aim for evolution rather revolution (hence my initial interest in minimal-change layouts). Of course, something like my mockup could easily be used with curved, angled or split designs just as the existing standard keyboard is, but at least if the kinds of features I suggested were commonly implemented, I think it would be a great improvement, while still not being too much of a radical shift!!