Both endings kick ass. And I interpreted the blueshifted object as a sort of protective counterpart to 1548.
Sorry for the long gap, but my internet here is spotty
I didn't really have an idea of what the object was while writing, and I still don't entirely. What I was really trying to get across with this is that 1548 may be one of the most physically destructive SCPs, but it's one of the least immediately threatening, simply because the Foundation has so much time to prepare for its arrival.
That, plus I love the classic 60s short story sci-fi twist ending.