Wearing a kill switch cable or tether in a boat can be difficult to say the least. If it was me I'd set it up with dedicated cargo areas, with walls, and dedicated control area for under way. In that second are build a false floor with lightweight coil spring suspension, like garden tractor seat coil springs or similar? Set up redundant microswitches, ala reed switch, that the ignition circuit is killed unless there's pressure of body weight of someone standing/sitting on that area of floor.

Also good to throw a trail line & float overboard whenever under way, something to possibly grab as a last resort.

Some have a spring loaded steering feature that when control is removed steering automatically goes to tight circles at idle speed. Carry enough spare gas to get home, plus some, and just let her idle herself until out of gas in a mishap.

Also good to wear a light rucksack or waist pack along with your vest in an extreme area such as that, so that if you do have something happen you have survival on you at all times.

Most local authorities will cooperate with you calling them, telling your return time, and that you will call back on return. If they haven't heard from you by XX hours, send HELP!