Melgarve is a beauty, isolated tarmac road right to the front door.
I think Cadderlie would be accessible from Bonawe on some good landrover track, spend the night on the shores of Loch Etive.
Pretty sure there’s a new one on the Ardgartan Peninsula, would be worth exploring as there is a very good network of tarmacked and gravelled forest roads on the eastern side of the Peninsula.
Good forest roads would lead you from Duror to the bothy underneath Beinn a’Bheithir.
Think Gorton has a landrover track all the way to the front door, and you could avoid the busy Glen Coe road by riding around Loch Tulla first.