What it says on the tin, either via something official or allowing Greasemonkey scripts. Being able to switch the mouse controls to keyboard would really help lower hand strain, especially for players with chronic pain or repetitive strain injuries.
Full support!! While I don't really need a feature like this I know it'd be extremely helpful for some, and even in my case it'd probably be nice (and good for my wrists haha) to switch it up a bit instead of always just using mouse. :]
Yes please, just thought about this as well, having the option for keyboard controls (preferably customizable) would be so important for accessibility.