This change would not be just be for backups or file transfers. It would fundamentally change how big files are stored by the file system. Much like the way fragmentation is handled solely by the file system and an application accessing the file is completely unaware if the file is stored within a single fragment or multiple fragments; the file system would manage the individual 'chunks'.
For example, a 6 GB file might be made up of 3 separate 2 GB chunks. An application might delete 20 bytes from the front of the file. This causes the first chunk to now be 2 GB - 20 bytes. The other 2 chunks are unchanged.
Current file systems do not allow this where a file can have a block somewhere in its interior that is just a partial block.
For example, a 6 GB file might be made up of 3 separate 2 GB chunks. An application might delete 20 bytes from the front of the file. This causes the first chunk to now be 2 GB - 20 bytes. The other 2 chunks are unchanged.
Current file systems do not allow this where a file can have a block somewhere in its interior that is just a partial block.