Hi dpaws,
I'm skeptical about your idea, mainly because I think it's based on some flawed assumptions, but I like the idea that you're having the idea and sharing it here. I don't think you deserve grief for that, although some robust answers are inevitable, so I hope that you weather the storm.
There's been a bunch of similar ideas challenging the conventional wisdom in narrowboat propulsion, none of which (in my opinion) come close to challenging it in reality usually because (again in my opinion) the implementation costs hugely outweigh the benefits. Nevertheless, I love the ideas. There are some actually out on the water, and 'NB Ampere' springs to mind as one. Not as unconventional as your idea, just a recent generation (sorry) of electric propulsion, but still unconventional at present. It's a beautiful boat to my own eyes and the systems are elegant from what I've read, but I'd be surprised if anyone would suggest it's really serious challenge as a mainstream power plant - yet. Possibly it's a folly, possibly it's a step in the right direction, but either way it's a welcome step in my view. Lest we forget, horses were the conventional power plant until someone came up with an idea to challenge that conventional wisdom. I don't think your idea will frighten the horses, but please don't let that put you off either thinking about it or sharing it with us!
Best wishes