5. I understand the need to add Cut, Copy, Paste, Undo to the left half to balance out the two halves, but if this was the primary goal, I'd suggest the following: expose Cut, Copy, and Paste in a cluster and above that have another dedicated cluster for Undo and Redo. To me, a dedicated Undo without a corresponding Redo doesn't make much sense. You could use the space currently occupied by the overly large Escape key, and turn Esc back into a normal-sized key (or slightly elongated key) directly above the tilde.
I used to think these side keys were useless. My opinion has now evolved after reading this.
Cut/Copy/Paste/Undo are all easily accessed with the normal ctrl+ shortcuts. REDO is not. If I ever want to flip back and forth, undoing/redoing, it's a hassle. So I can now see a reason for these side keys: Providing a block with Undo and Redo.
I still predict that these keys will be unusuable when mashed together in one block. There is poor muscle memory learning this new layout, and it seems error-prone.
So I think the design would be better with Undo+Redo next to each other, then a space, then Cut+Copy, then another space, then Paste. You will pay for this extra space by making the Escape key a normal size, because it does NOT need to be huge. It is not frequently used, plus it is easy to find, so a smaller key is fine.
Illustration:
Esc
Undo
Redo
Copy
Cut
Paste
Fn
After thinking this through, this is the first time I've thought I might actually USE this kind of shortcut block on a custom keyboard. But the spaces are required, and the undo+redo is required, to get me on board.