That sounds like a viable option for you
and your wife. What I recommend is that you determine how far you may need to go in an emergency, assuming you've used the motor regularly and are as far away as possible from the nearest point of refuge and/or assistance, then figure out how many batteries you'd need to make that motor get you there. If you can accomodate those batteries in your boat, that gives you an idea of feasibility. Once you do that, you will be able to determine if that is the right solution for you, since only you know your boat and how far and where you plan to cruise.Conceptually for the challenges of engine starting that you face, it is a good idea.