Doing this efficiently requires the adoption of more filesystem internal
transaction processing techniques - meta data undo in particular.
However, "transactional filesystem" usually refers to a much more
complicated setup that allows an arbitrary number of data and meta data
operations to commit or rollback as a group. That is an order of magnitude
more complicated than what would be required to efficiently preserve the
atomicity of file rename operations, for example.
That might well be standard a couple of decades down the road - Google
Transactional NTFS for an example - but for now the ability to provide
atomicity without durability would be a major improvement that has a
fraction of the complexity.