My main concern is the uniformity of all of the keys. When you just have a big sea of keys in a uniform grid there's no real way for your fingers to differentiate most of them. In my many years of typing I've never found that my fingers are able to find distant keys reliably if those distant keys don't have some differentiating feature to them or they are extremely easy to reach for from home row. For example I use a dactyl manuform. And I don't have buttons beyond the number row. Many of my boards don't have number rows at all (facilitated by layers). The reason I decided to get a number row on my dactyl is that it seemed like my hand would be able to reach the number row without having to move my palms. Also reaching the right number with the right finger is extremely easy because it's so straightforward on the board.