Well...actually as long as the motor is off you can shoot from a boat, and Stehekin is NOT the same as hunting along the shoreline of the lake...the lake is 55 miles long with at least the last 30 in national forest. Stehikin is the small community that is a jumping off spot for trail hikers and NPS workers/visitors. So your assumptions about Stehekin are correct, but as for hunting along the lake, that's a different story...north shore (south facing slopes) is steep with lots of snakes, very few deer down low, and the south shore (north facing slopes) is rocky cliffs and lots of bears but fewer snakes! But keep in mind that there are a lot of small private parcels along the lake and most docks are private, and those that are public now require a use permit (Until Nov. 1st...or maybe it's Oct. 1st...either way, check with the Lake Chelan Ranger Dist). Oh, and if you are thinking about just anchoring up or tying off to shore, keep in mind that there are places along the shoreline that are 1,000 ft deep, yes, 1,000 ft...(look around the shoreline along Point No Point or Falls creek...sheer cliffs down 1,000 below the water line.
Basically, there is a reason why very few people do this hunt...and it's not because people haven't thought of it or tried it.
Lastly, you don't need a boat, the lady of the Lake will transport you and drop you off at any location you like (they have a gang plank you can use on the bow, yes, the water along the shoreline is that deep, they can put that boat within 6 feet of the shore and not touch bottom in places). but they are getting stricter on guns, and dead animals on the boat...be sure to give them a call. If you try and rent a boat keep in mind that most rentals are stopped after Labor Day and even if you could find a place to rent you a boat most don't allow you to go past the Narrows...which will put you about 35 miles from Stehekin.
Grade
PS. Good luck and keep us posted!