Reordering base level nodes

Summary

How best to reorder base level nodes while preserving custom sorting on parents

Content

My client wishes to have all base members under a given parent sorted by default order (alphanumeric). But upper levels need to retain custom sorting. I do not see an easy way to accomplish this in EDMCS. I need to enable Custom Sort Order on my hierarchy set to retain the proper sorting of parent members. If I disable Custom Sort Order, my base members are sorted correctly but not my parent members. Has anyone come across this or come up with a clever solution?