This would be a great option to have in order to aid in minimizing future fragmentation. Grouping less frequently modified files at the beginning of the disk would create large swaths of used blocks that are less likely to be modified, while others are placed near the free space at the end. Then you'd effectively have two sections of files, 1. likely to fragment and 2. likely to be still; after some usage, the second section of files would probably not need to be defragged again as they haven't been modified.
Combining this with types of files would be even better I think. For example, an exe file will probably never be modified, so that type can override the date and be sent to the beginning of the disk regardless of modification date. The same can be said of DLLs, archives, blob, etc...
