There aren't a huge number of ready loops to be done out of the main Bitterroot Valley, at least without bushwacking or ridge scrambling. If you can find someone to do the rather long shuttle to the start, I'd do a through hike from Selway Falls up the Selway, up Moose Creek, then over the pass and down Blodgett Canyon. The Selway is gorgeous, Moose Creek has some stunning, massive cedar groves, and Blodget provides great rocky alpine scenery. This might push your mileage limit a bit, but most of the walking is quite easy.
Casey Greene knows the area better than I do and might have some good ideas.