This is what I would do. I don't like the looks or placement of most mounted ladders. There is one that mounts to the the jackplate that I've considered but dang they're high for a piece of metal. Thought about a portable one just to hang over the side when it's cold but doubt I'd ever put it in or remember to take it.
I seen a homemade rope emergency ladder you just toss over the side but can't find it. Maybe if I can find it again I might try that as a back up to the motor?
Found it.
DIY Rope Ladder, Boat Emergency Rescue Ladder, Rope Only. - YouTube
BetterBoater.ca - Rope Ladder - YouTube