Working on a post, but first, in case I need to know,
@LokiLeo789, is Xerxes aiming at Anaru's last remaining ship or Freya's incoming one?
Also, to weigh in on the idea with the Massacre Pirates getting sent to Impel Down
@Ira, it doesn't sit well with me for a number of reasons:
Firstly, it's probably on the other side of the world. If the Conomi Islands are closer to Loguetown/Reverse Mountain than Impel Down is closer to Mariejois, which is on the opposite pole. That is a crazy long voyage for some small time prisoners. To give a canon example, Arlong was not sent to Impel Down from the East despite being a former prisoner as we saw in the Fishman Island flashback.
I think the biggest problem though is that if the Massacre Pirates are sent there, then narrative insists that they must escape. And if some literally nobodies from the East can escape the greatest prison in the world, then now it's been reduced to DC's Arkham Asylum: a revolving door for players who'd had their characters captured. Prisons in general were always going to be like this in the event of a capture, but Impel Down?
Also, even if they somehow do escape, now they're stranded in the Grand Line, leagues away from any other player characters, unless they go back, which trivializes the long journey everyone's supposed to be taking even further.
I think the best option would be to just create a high security prison in the East to break out of. You'll have more freedom with the setup/layout, and breaking out won't undermine an important setting landmark.
...That ramble is going to end up being longer than my next post, isn't it?