I rather like this idea, because otherwise, you'd have the first three Symphonies, then a completely new title image, which'd be a bit jarring. Besides, it was mentioned earlier that the way S4 ends is an appropriate close to the Symphony of the Sword in toto, and I am therefore quite pleased with the reorg, especially since it simultaneously solves the rather long sidetrack into Dìqiú.

Besides, there's a timeskip in S3 anyway, which is actually longer than that from the end of S3 to the beginning of S4, and if S4 moved to the opera, then the SOS would end with Lion of Avalon, which is kind of an odd note.