The problem with this type of combined system is that it would entail pretty significant compromises as either an outboard or a towed generator, or both. And frankly both systems independently are only moderately successful. Towed generators create a lot of drag and reduce speed significantly on cruising boats already, ough they do provide a lot of power when working. And electric outboards... Well the best I have heard an owner say about one was "meh" they work but aren't stellar performers.
I am afraid you would wind up with a system that is the same price as the two combined, but didn't perform half as well as the other options.
On the distributed power... There are, and have been systems that do that on the market for years. The problem is it really takes a full rewire to justify it as a refit, and builders are slow adopters.
Correct on both points, Greg. Tho people will continue looking for alternatives to the gasoline outboard as long as those keep letting people down so often.
Some European custom builders are using more sensible wiring architecture -- not least because copper has gotten so bloody expensive. You can't be running 60' of 2/0 hither and yon. And some bow thrusters are already working off their own dedicated battery. It is a good solution for high-amp loads used in short bursts, with plenty recharge time in between. Like a windlass, or a thruster. If you only need an outboard to run your dink to and from shore -- versus exploring up river, or visiting dive sites two coves away -- an electric outboard is an okay solution. (But then, so is a pair of oars....) In which case, having a spare battery pack is handy. In which case, why not double its utility as the windlass batt?
Right now, I'd faint with gratitude if the industry would finally admit 12V is a stupid idea and upgrade to 24 or 36V. I'm told 48V starts getting too close to lethal for boat use, but sheesh. Who is gonna move first -- manufacturers? Electronics makers? Alternator builders? Europe is again ahead of the US here, but wiring boats to 12V is as dumb as wiring tractors to 6V was. We WILL be completely rewiring our boat, but too many systems are still clinging to 12V for us to mess with converters. Unless something changes radically in the next 2 years, we are stuck rewiring to 12V.