Dalwhinnie to Corour would tempt me under those criteria, but would probably need a tent. Ben Alder bothy possible, though a bit off the direct route. Loch Ossian YH a bit too close to the finish to work. I do like a through route, though!
Ardlui to Bridge of Orchy on the West Highland way is a possibility which goes through rather less remote country. Overnight in Crianlarich in B&B or YH. You'd need to check the little foot ferry from Ardlui to Ardleish was running at the time of year youre wanting to do it, otherwise the start doesn't really work.