FAT manipulation?

Yipe.

I understand the principle and why you suggest it but it scares me to trust someone else to manipulate the FAT.

Microsoft I have to trust, but a third party?

The files only really need to be stitched together when all are complete. That's only a single job.

I am prejudiced because I'm running a striped array. The stitching doesn't cause me any great problems. If FAT patching was implemented, I'd want it to be an option I could turn off.