The many-button mouse is appealing as way of reducing movements between mouse and keyboard. But it's even better to just stay on the keyboard and skip the mouse altogether. Mice have to be the number one source of computer-based tendon injury. Fortunately, the standard laptop is relatively "ergonomics".
The standard laptop is hardly ergonomic. The trackpad and pointing devices are somewhat helpful but the keyboards are all (without exception) terrible for extended typing. You're much better off getting a separate keyboard with the left and right halves of the keyboard angled inward so that hands and arms can remain in alignment.
But in general, I don't see anything keeping a person from holding their hands in alignment over a standard keyboard and typing. Any keyboard does involve small finger movement to hit the different keys, so a can't see how changing key layout changes anything.
Each person has a somewhat different pattern of habitual tension that can interfere with even normally easy activities, so there are many adjustments work well for some but not for others. Mice are a different story in that they require arm movements for simple input, an inherently inefficient setup.