You can reprogram virtually any button (keyboard, MIDI key, mouse key, etc.) to carry out any number of pre-defined actions.
Driver configurations can be used to change the default behavior of a
keyboard or mouse that uses ControllerMate's driver.
All buttons on a keyboard have some default function or ...
Option 1 - Build your own mount
The only way I could see getting either a new stand or a VESA mount is having a custom VESA mount built for this unit.
It's actually not too difficult to build the mount, you just need a flat piece of aluminum or stainless thick enough to attach to the mounting plate of the hinge (area circled) in pic below and long enough ...
Inexpensive - no way to modify the Mac. Instead modify the table or change chairs or what the person stands on. Those are all far less expensive to customize.
The expense of opening or modifying the Mac is the self-insurance you need to set aside if you damage and/or break something and have to pay for it to be fixed professionally. Not all open/repairs ...
We can separate the possible solutions into intrinsic and extrinsic solutions, as well as sitting/standing solutions.
Intrinsic solutions (ones that will not look like an afterthought):
You can "[b]uy [an] iMac with Built-in VESA Mount Adapter". You will not see this option on the usual checkout lane, but Google locates it.
The 27" iMac weighs 21 pounds (...
When I need to hit command and either control or option,I generally use my left middle and fore fingers, sometimes middle and thumb, sometimes pinky and thumb.
However, it's not especially often I end up needing more than one modifier key at the same time (ie, I usually only need command or option or control with another key - not together).
If by ergonomic keyboard you mean a split keyboard, you can do this natively on the iPad.
To do this:
In the bottom right corner of the keyboard there is a key with a keyboard icon (with a black down arrow)
Tap and hold that key
A toggle for the split keyboard will pop up (or, if it's already split, a choice to unsplit the keyboard will appear instead)
I used two options, both based on a vertically adjustable keyboard "tray" (not really a tray, just an adjustable portion of the desk meant for the keyboard):
Option 1) I used 3" length thread stock to extend/raise, rather than lower, my keyboard portion of the desk. Then I simply raised my body to be ergonomic with the keyboard and iMac display - my chair ...