A lot of accusations for a name spelt into a wall. If something did happen to Cassandra, what could she say that Arms Slave did? It's not as if he had a smoking gun. Motive? Sure. Means? Likely. But culprit? No more guilty than any other outlaw who was at the battle and holds a grudge. 

Now there is one thing you're right about: Retsu would be pissed. Which is why I want Dark Wraith and Eclipse Princess to meet. In sure they have much to talk about, and dare I say, even a similar goal. Or at least a minor wish that would be pleasant to achieve.