I was thinking a bit too much about this today at work, and I think I've come up with enough locations that we'll have to do three or four trips over the course of the winter to even scratch the surface. Some of my ideas...
1. Stratton Mountain and Pond, VT-- great base camp area near Stratton Pond, with challenging hike to Stratton Mountain for the dayhike. Maybe not too secluded, though.
2. Glastenbury Mountain, VT-- Not sure about the approach, but the summit is pretty cool, and there's a fire tower that we could camp right next to.
3. Pemi Wilderness, NH-- So many options in here. One really nice one is near Norcross Pond on the east side of the wilderness. Or the west side, we could hike in from Lincoln Woods and do a dayhike up one of several mountains.
4. Griffith Lake and Baker Peak, VT-- another possible base camp further from the road, with an easy-ish hike up to a good view.
5. Wild River Wilderness, NH-- Lots of good places to camp at low elevation, and then either hike up to Carter Dome, Moriah, Baldface, or other cool mountains.
I've totally left out the Berkshires, which would be a fine location as well.
I'm partial to trying bushwhacks, too, since winter is the time for that in New England (as far as I'm concerned... less undergrowth). And we can come up with trips ranging from one night to five or six if we feel real crazy (or unemployed).