Hi Ben,
Last year I planned to walk the following route:
http://afstandmeten.nl/index.php?id=2363585. From km 9 to km 31 this looks roughly your route, except for leaving out the first summit. Based on satellite image, this route looked doable and a bit path-ish. But when I was at the Blackwater dam last May, because of the extreme hot weather, I decided to not go south over the dam and further to Rannoch Station, but north east to Corrour, as that would give more reliable water supply and shorter to the station. Was a splendid day out, but did not learn the route south of Blackwater.