I have added this request to the tracker:
Issue 2111 – Continuous allocation of disk space for local files
You can vote for it there.

What ever became of this request?
SetFileValidData, contiguous (non-fragmented) files with no allocation time

I have lots of small files and all large files fragmenting. Not a big deal with an SSD, but I don't have a SSD. The old and still in major use program RSYNC can pre-allocate.