How about…
Blair Atholl – Allt Schiecheachan Bothy (train to Blair Atholl the night before day 1)
Allt Schiecheachan to Tarf Bothy via Beinn Dearg (day 1)
Tarf Bothy to Ruigh Aiteachain bothy via An Sgarsoch and Glen Feshie (day 2)
Ruigh Ateachain Bothy to Aviemore via Sgor Gaoith and Mullach Clach a Bhlair (day 3, train home from Aviemore)
Nice round Cairngorm hills so easy backpacking 😀
or….
Tomintoul – Loch Builg (wild camp, day 1)
Loch Builg – Faindouran bothy over Ben Avon (day 2)
Faindouran Bothy back to Tomintoul via Bynack Mor and the Water of Caiplich/Water of Ailnack (day 3)
Slightly bigger days, slightly wilder
or…
Dundonnel to Carnmore Bothy (or better yet wild camp high up somewhere)
Carnmore to Lochivraon Bothy via A’Mhaighdean, Ruadh Stac Mor, Beinn Tarsuinn and Mullach Coire Mhic Fhearchair (big day with 20kgs though, and some scrambling)
Lochivraon to Dundonnel via ‘the white mile’, Sgurr Ban, Beinn a Chlaidheamh and Achneigie
This would be spectacular if you got the conditions but would also be pretty punishing unless you’re fit and carrying lightweight gear, it is/was a pipedream of mine if I ever shake off my various niggling knee injuries…
A circuit of Loch Monar is 42km with a pretty tasty looking horseshoe of Munros at one end, you could even descend to Bearnais Bothy at the natural halfway point of the horseshoe. Haven’t figured out the logistics at the other end, think the Landowners are a bit stuck in the past regarding access along the road to the start of the loch…