Anyone with a device have any guidelines on how fast a player can reasonably be expected to turn the crank?
I don't have any real guidelines, but subjectively the fastest I can comfortably go is about 20 revolutions in 10 seconds, or 2 revolutions a second. obviously depending on the circumstance I can go faster, up to 3 revolutions per second, but it's going to be subjective player to player.
This is my moment to shine.
Please be aware that not all players are created equal.
Panic actively promotes designing your game for people with disabilities. Think of flipping the screen and controls, which is possible from the system settings.
Inclusive design benefits all. Think of dark mode on a smart phone. Originally dark mode was intended to help ppl sleep or see in the dark, but it can be a great help for people with visual disability too.
I would say: also map alternating up/down and left/right and a/b presses to whatever action is controlled by the crank, if the buttons are not required for other actions at the time.
And in your game settings, add a cranking speed setting.
For sensible defaults, look at other comments in this thread
In terms of physical ability, having a setting to turn down in terms of physical ability would be a good idea too.