The AP on my
boat is engaged and disengaged by a toggle switch that is at ankle level inside the
cockpit. Handy to turn on and off but can be accidently toggled by a stray foot. The first year I had the boat the AP was accidently engaged without my knowledge (probably by me) and I turned the wheel to change course, and on meeting some resistance gave the wheel a tug. Broke the tiller attached to the
rudder stock! No damage to the hydraulics or the
steering cables, pulleys etc. but I was pretty surprised as the tiller was
bronze and seemed quite skookum.
No wonder serious damage can be done to body
parts, your concerns are very real.
My solution has been to educate all concerned but also I never leave the wheel unattended (I always sit right behind it, as is done while driving a car). If I leave the wheel I ensure whomever takes my place is made aware of whether the AP is on or off. I have also rectified the possibility of accidently engaging the AP.
On a lighter note I was leaving my overnight berth in Coal Harbour a few summers ago. I had taken the wheel off the evening before as we had a fair crowd in the cockpit. I jumped on board after pushing off and found to my surprise that the wheel was still tied to the lifelines!

A fair bit of scrambling ensued but I was able to safely exit the marina without damaging any of the megayachts. Haven't added checking to `ensure wheel in proper location` to my checklist but not a mistake I expect to repeat!