Therapy - you are right , of course.. it is better to make it perfect. However, it has worked for 30 years with the current wiring, and is still floating. If I improve things by changing the feed from 14 ga to 10 or 8 ga, for example, it will ceratinly be better than it has been (for 30 years).
re: emergency, yes some things like running lights, steaming light, bilge pump and electronics could all be used at once. But I doubt that I would also "need" to turn on the water pressure pump, anchor light (assuming we are moving), all five or six cabin lights, etc, during an emergency as well. So I think that some common sense can be used in determining wire size.