FastFill(gapsize(n))

I think FastFill(gapsize(n)) could be a good complement to Defragment(chunksize(n)), FastFill() and FastFill(Withshuffling).

FastFill(gapsize(n)) would refuse to only partially fill the gap, if it would leaving a gap smaller than gapsize(n). ( gapsize(n) I suggest 1-2 x chunksize(n) )

Edit: variant - will not refuse partial fills, but small residual gaps will be further processed.

If there is already a gap smaller than gapsize(n), it would try to fill it normally if possible.
Otherwise it will be enlarging it until it either finds perfect fill ( as Withshuffling does )
either a gap has size gapsize(n) at least.

The result will be avoiding small gaps, that leads finally to defragmentation of big files even by Defragment(chunksize(n)). And it also avoids excesive gap enlargement by shuffling.

In conjuction with that, files should not be moved away from a gap in bigger chunks than gapsize(n), if leaving big enough rests of files. IMHO this feature could be especially useful for data partitions with big files like multimedia, CD/DVD images, archives, virtual disks.