I don’t think we’d ever want to do that, since it would reduce the granularity available when making adjustments. If your current subtitles are really 10 seconds off, then you might actually be better off getting a different/better subtitle file. You could always make use of the on-demand subtitle search functionality.
Now, all that being said, we do also have some other work in this area of subtitle timing in progress. No specifics to share just yet, but we think folks might find it pretty exciting once it’s ready to release.