For some source/destination combinations it may be possible to copy data directly from one cloud to another without copying the data through the machine running rclone. For example, it is possible to copy data from Google Cloud Storage to Azure by passing either a public URL or Signed URL to the Azure CopyBlob operation.
This has the potential to be significantly faster, particularly for large files, and when the computer running rclone has limited upload bandwidth. However, it can only be used in some situations and is incompatible with some rclone features (e.g. bwlimit, timeout). It would also require some significant internal API changes to expose methods for negotiating and initiating direct transfers.
Is this an approach that you might be interested in pursuing? Or is this outside the scope of what rclone aims to do?
Thanks for considering,