Re: Optimal propulsion system
"The hunter e33 has this as an option"
Only one problem, Hunter's parent company are now out of business, so you'd have to try finding a leftover or a used one.
I don't see generator noise as being as issue since one of David's criteria was "not missing a slip assignment" which means he can just plug in and recharge at the end of the day.
Find a Chevy volt, gut the drivetrain and the very economical generator from it, and voila, the rest is just wrenching. Especially if you can plug in most nights to recharge.
Short of that, I'd wonder if new engine mounts (after 5 years they've stiffened up and make for a noisier shakier boat) a shaft isolator, balancing, and some engine bay insulation might not be the best ways to tackle this.