Enough with the black-out text! Here be SPOILERS on how to improved the storyline of WotVB!!!
[you were warned]
Khur: "After Garrow rams Cloud's Destiny, it's unlikely he survives the crash of both ships (average fall damage 42, Garrow's hp 32)--at least as he's written in the adventure. The flimsy advice on page 22 (Garrow always has an escape plan) is simply sad—a DM needs to know how he escapes. The solution is as simple as giving him and his key personnel feather tokens or other fix (ala Cloud's Destiny's)."
Potion of Feather Fall resolves this. Since Garrow is described as always having an escape plan, he'd be unlikely to comandeer an airship without some means of bailing out. His personnel can steal more on Cloud's Destiny.
Khur: "Your scheme also fails to explain how Scimitar knows the PCs' location when they take the lightning rail. If it's divination magic, it's powerful stuff, having anticipated the loss of the airship and the PCs' trajectory after the crash. So, Scimitar's appearance on the rail still makes no sense at all from the presented storyline’s standpoint."
Every warforged could be a potential spy for the LoBster. All it takes is one warforged to hear about the party's journey from Sharn to Trolanport and ask a few questions about what happened at the docking bay of Cloud's Destiny and messages could be sent to Scimitar to aprehend and slay all but one of the PCs. Final messengers, whispering wind and other means of communication are available to the Lord of Blades. And Scimitar could be trailing them since Saber's (or Cutlass') death. Or since the PCs ventured into Whitehearth in SotLW.
Khur:"As an aside, why would BoV rely on such a flimsy and expensive scheme to kill the heroes? Much simpler clean-up scenarios exist that needn't leave the area of Sharn. Further, if the Emerald Claw are using this as a plot against the heroes, what happens when the PCs jump aboard Jade’s Fury after missing Cloud’s Destiny? I’ll tell you what happens: adventure over as the Emerald Claw kills the PCs aboard Jade's Fury. Your point about Garrow's jealousy may be able to explain this away, though."
But the Emerald Claw isn't out to kill them outright. They want to learn all they know about the schemas. If the PCs board Jade's Fury, Rorwag asks questions trying to ascertain what the PCs know. After they are sent to Cloud's Destiny, Rorwag orders his raiders to attack and kill all the PCs (since he knows how much they learned on the schemas) and also to kill Lucan (who he hates). The original plan was to ambush the PCs at the ziguratt and have Lucan turn at least one into a vampire minion, but Garrow won't allow Lucan to do that, fearing for his standing in the Blood of Vol. With some eyes-of-the-eagle item, he keeps tabs on the fighting, and as soon as he sees the PCs overpowering his raiders, he snaps, ramming the other ship, quaffing a potion of feather falling and bailing out. He hopes the fall will cover up his selfish attempt to destroy the plan of turning a PC (or all) into a vampire.
Since Lucan doesn't know Garrow caused the crash on purpose, he assumes the PCs are responsible, and improvises. He takes the Lightining Rail and jumps off when he closes in on the ziggurat. He arrives, expecting to find Garrow and the other Emerald Claw soldiers there to back him up, but these never arrive. So he makes a last stand, severed from humanity, abandoning his sister and (apparently) betrayed by the Blood of Vol.
Scimitar and her strike team (I'd leave off the halflings, though) want revenge on the PCs and are instructed to take one (and only one) alive to the Lord of Blades. Her sudden attack on the Rail makes Lucan even more nervous. And you can have Garrow (disguised as a passenger) witness the attack and approach Scimitar after the PCs jump off after Lucan.
Oh, and the Dark Lantern commander that hires the PCs in the first place? Also Garrow. If/when the PCs return with the sword, they find the address empty. If they ask about the commander, they learn that the commander has been away on a diplomatic mission for the past month.