I'd add tenting / tilting support to that list, along with good physical key placement, especially on the pinky columns. As an example, on the Keyboardio Model 01, the pinky columns are positioned lower than on - say - the ErgoDox. This makes the keys (think P, for example) easier to reach with shorter pinky fingers. Also, when designing keys for the thumbs, keep in mind how many one can reach and press without also pressing another, or having to lift one's hand. The ErgoDox thumb cluster is awful in this regard, there are 3 usable keys there only, and 3 others almost wasted.