Thought about the Schehallion path myself as it is only about 5 miles from me. From what I remember last walking it over a year ago it has a lot of big water bars, and is one of the most popular walks in the country so you will encounter an irate walker every 10 metres at the weekend.
Not sure about the path condition these days, but to truly appreciate the awsome desolation of Rannoch Moor, train from Rannoch Station to Courrour and cycle back. Not technical but stunning scenery.
Also, there is a path from Rannoch Station to the Blackwater dam, and you could then do the Ciaran path down into Kinlochleven. No idea if its ridable though.
For a really stupid day out, how about train (or cycle) to Corrour, down Loch Ossian, take the glen (don’t have any maps with me) towards Ben Alder, do the Bealach Dubh circuit from half way round, and then back. About 45 mins pushing up the glen and back.
Sorry, not much help but may give you some ideas