Any hot swappable ergonomic board will be fine. Hot swappable means the switches can be pulled out of the sockets on the circuit board. Otherwise, you'd have to desolder the switches.
Edit: Do not worry, assembling a keyboard from parts is childs play. There's not a lot that can go wrong, just be careful not to damage the circuit board, and check that it fits the case.
Thanks for responding to me... I went into a deep dive, since I didn't know that was a possibility. Unfortunately, there are no full-size split hot-swappable ergonomic boards.
I can deal with a separate numpad, and I can use shortcuts to replace media/brightness/volume keys, but you can take away my arrow keys when you can pry them out of my cold, dead hands ;-) I'm not ready to go the chording route of something like the ErgoDox.
I found the Cloud Nine C989M, not hot-swappable, but ANSI layout only, no ISO, so it's out of bounds.
The Keebio has the Quefrency, which I can kit out with a separate numpad and wrist rests, but that's not hot swappable, and 1.5 to 2x the Matias Ergo Pro.
I think for now, it'll have to be the Matias, and maybe later I'll decide it's worth the investment to go chorded, or invest 4x what I'm used to (as opposed to 2x)
