I'm not saying it wouldn't work, but for me being from Germany the keyboard is even more expensive than it is anyway and I'm not sure I'm willing to pay that much for the hope that I can adjust to it.
[1] https://configure.ergodox-ez.com/moonlander/layouts/mzD9d/la...
[2] https://configure.ergodox-ez.com/moonlander/layouts/60ynN/la...
[3] https://configure.ergodox-ez.com/moonlander/layouts/jXjMx/la...
This is my ErgoDash layout. I have one less bottom-row key than the Moonlander, so I have combined PgDn/LeftAlt and ←/RightAlt onto single keys. I would uncombine these if I had the extra key, as I occasionally press Alt when I intend to press ←, but am too slow.
I also have Enter/Ctrl as a single key, but it's very rare for this to do the wrong thing.
http://www.keyboard-layout-editor.com/#/gists/501437fce9123e...
I mostly learned the layout to reduce stress on my hands due to the more ergonomic placement of each letter.
From all the other layers I only use the cursor keys and L3 for []{}<>() and stuff like that, which are much easier to reach and I use a lot when programming.
The magic is the double use of modifiers if tapped or held.
Whilst I personally could see a need for another column if you have a Nordic layout like mine, but that would make it not symmetrical and unnecessary for English layouts.
[1] https://configure.ergodox-ez.com/moonlander/layouts/rOjGj/la...
As for using a navigation layer - perfectly happy with that 90% of the time, I already use that today, but for some things I just prefer actual cursor keys. For example selecting an entire word in an editor, you press shift to select, ctrl to jump a whole word and cursor for the direction to jump in. If you add a modifier to that, you start breaking fingers ..
[1] https://configure.ergodox-ez.com/moonlander/layouts/60ynN/la...
I have ← ↑ ↓ → in a line on the four lower keys on the right of my ErgoDash. Not having the ⊥ arrangement took a little time to get used to.
I considered some fancy QMK (keyboard firmware) hacking to keep the inverted T, and have the key above ↓ change between Z and ↑ depending on the keypress before, but decided it wouldn't be practical. However, the Z is for Dvorak. A Qwerty layout, where it would be /, might cause less trouble.