I suggest removing the tabs as well, going back to the old layout, and then add the option to not have a horizontal split, but a vertical split. it would be much more efficient space usage for widescreen displays, as most are nowadays.
That way, the file list would be completely from top to bottom, and the fragmentation-display would have quite a big view area, allowing for a good detailed view what's going on.
Oh, and some options would be nice, like, not reporting that some files could not be defragmented. I can see that in the file list myself (It could get highlighted, thought).
I can set up a fake image to show my idea.