I too have been intrigued by this topic, I am certainly no expert however I have done a good deal of research.
Simplistically an electric motor can easily replace a diesel motor, however diesel is a far more efficient store of energy than a battery. This then begs the question of how large a battery bank one can have, and how do they get recharged in order to be effective.
In my research it seems that the best solution would be a solar array, wind generators, lithium ion batteries and a diesel generator along with the electric drive motor. This configuration balances weight and performance, allows for similar to greater range, probably supports greater house electrical consumption.
Lithium ion batteries are much lighter or provide greater energy density so that for similar weight to current batteries one might get 2 to 3 times the power storage. Also Lithium ion batteries are more efficient to charge and discharge, however they are still a lot more expensive than traditional batteries.
The number of solar panels and size of wind generators one might want to or are able to install will impact the total energy availability on the boat. It seems to me the sweet spot seems to be sizing batteries to accommodate motoring for 3 to 6 hours, but still provide essentially unlimited range. Thus would essentially come close to achieving your goal, but protect you from cloudy windless days and extended periods of motoring. Think Prius instead of Tesla.