On the north shore of Attean Pond in Jackman, ME, there is a trail to Sally Mountain. It was fairly conspicuous and near a couple of primitive campsites. We did not hike this mountain ... after all, our destination was the Moose River Bow Trip and the 1 1/2 mile portage between Attean and Holeb Ponds meant 4 trips = 10 miles "hiking" after less than six miles paddling. The trail is about two miles from the Attean Landing launch and crosses the RR line so that would be another route for access ... but watch out! it's an active line.
Lobster Lake, near Moosehead Lake, has several primitive campsites and a trailhead to Lobster Mountain. Haven't been there yet but am planning a trip to include this hike and a paddle down the West Branch at the end of August.
We've scouted out Flagstaff Lake and the landing and trailhead to the Bigelow Range, which is also accessible by vehicle. We plan to do that, probably in October, with a base camp at Flagstaff Lake Hut where I believe they have kayaks or canoes available.
The northeast part of Squam Lake in NH is a comparatively undeveloped area on a comparatively peaceful lake with a trailhead at Five Fingers Point to Rattlesnake Mountain which also has a trailhead across from the parking lot to Morgan/Percival.
Interesting question ... combining a hike with a paddle, especially one exclusively accessible by boat ... is always in my mind as I look over maps and guides. Please let us know whatever else you find.