Then is the solution to have write-only be the default for muts, so that they start out write-only at least, but can also be made to be read-write either (a) in

Then is the solution to have write-only be the default for muts, so that they start out write-only at least, but can also be made to be read-write either (a) in given circumstances of creation, or (b) after certain operations on them, or (c) if created by certain APIs?