I don't doubt that many people would benefit from alternate keyboard layouts. I would have thought that the many DIY esoteric keyboard projects cater for that segment. Or you could buy a DAS keyboard with blank keytops and reprogram the key positions to suit yourself.

Personally I learnt to touch type decades ago. 99% of my work doesn't even make me reach for function keys, nor the cursor keys. (Ok, I'm a vim user). The escape key is the same as CTRL-[ so it's very easy to type quickly. I rarely look at the keyboard, I just watch text appear on the screen.

In my experience, it is my thinking, reading and comprehension speeds that slow me up. I can type fast enough when I know what I'm trying to write or program.