Tom,
I don't think your requirements are too 'out there'. Seems to me there are just a few constraints on your project. 1) You must be willing to accept slow speed and maybe even no speed (i.e. don't go) when adverse wind or current conditions occur. 2) Recharging from shore power must be convenient because that's the energy source that's cheap and quiet. All the other options, when sized to be practical for every-day use are either very expensive or bring with them the downsides of ICE power. Plus most of them would work better driving the prop directly instead of the daisy chain of prime mover to generator to battery to motor to prop.
I could see a long narrow light hull ( a catamaran would be even better) optimized for a speed/length ratio of perhaps 0.6. A boat with a 30' waterline length, weighing 3000# with (16) 220ah 6v batteries could go 140 miles at 4 mph.(11 amps at 48v) 100 amps would give 8 mph for 22 miles. Total battery weight would be about 1000# and cost maybe $3500 for top of the line AGMs. Maybe 1/3 that for wet batteries. You could cut the bank size in half in you were happy with less E range or more reliance on a gen set.
A 2kw quiet generator like Honda EU2000 ($900, 50#) hooked to a 1.5 kw battery charger would drive the boat about 5 mph with no battery drain. You'd want the generator out in the open for cooling and gasoline safety. They are not marine rated and not safe in an enclosed area. They are very quiet though, I'd say as quiet as a little four stroke outboard. It could recharge your 80% depleted bank in about 15 hours.
You stated you don't want a 'regular' sailboat with aux E power. Just about anything will sail down wind, though, and that's what I'd set up, making the rig easy to strike when not sailing. A 150 sq ft balance lug rig would have spars short and light enough to be taken down and stowed without any mechanical advantage (build them hollow) and would perform well off the wind. You don't want any foils sailing down wind and a simple lee board would give you a modest reaching ability.
Denny Wolfe
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