Channel72 said:
Even if Lucas was toying with the idea of “Father Vader” before Brackett wrote her draft, the idea was still sort of clumsily forced into the script, giving the impression of a “last minute rewrite”. The fact that Vader apparently is okay with KILLING Luke at the beginning of ESB is a vestigial remnant of the original script, where Vader very much explicitly really did want to murder Luke: there’s a scene where Vader tries to force choke Luke to death as Luke escapes Hoth in his X-wing. This early motivation partially carries over into the final draft, when Vader orders the orbital bombardment; Vader’s actions were never properly updated to reflect the later revelation at the end.TLDR:
The original arc for Vader’s motivation was: “(1) Find and kill Luke, (2) Change of plans: capture and convert Luke to appease the Emperor”
The UPDATED motivation in later drafts was: “(1) Find and kill Luke, (2) Change of plans: capture and convert Luke because Luke is his SON, and can be used to overthrow the Emperor.”
But in everyone’s head-canon, the motivation is more like “(1) Discovers Luke is his son, but hides this from the Emperor, (2) tries to capture Luke to overthrow the Emperor”
The head-canon version at some point became ACTUAL canon via some Boba Fett comics. The head-canon version also makes the most sense given the “big reveal” at the end of ESB, as well as the wider context of Star Wars lore. But the head-canon version just is NOT supported by the first act of the actual movie.
I really do appreciate all the thought you’ve put into this so I hope I don’t come off flippant at all, but I think your concerns over the plot’s integrity stem pretty much entirely from an assumption that Vader for sure would have order the “orbital bombardment” and that this would entail the instantaneous extermination of the rebel base and its entire population. General Veers simply informs Vader that the Rebels have a shield up strong enough to deflect anything their ships can throw at it, and Vader is perturbed that this means the Rebels already know they’re in town. We don’t actually know what Vader would’ve done otherwise or if the rebels had any other defenses against being fired on from space. (if there’s a script weakness to this scene, it’s more that you can just feel the plot contriving itself to accommodate its spectacular land battle sequence, but would we have it any other way?).
As far as the Hoth battle itself putting Luke’s life into potential jeopardy, I also get the sense that Vader and The Emperor don’t believe Luke can be taken out randomly in battle. To them he’s a mysterious phantom youngster who inexplicably showed up out of nowhere and blew up their Death Star, he’s caused a “great disturbance in the Force,” etc. They know if he is to be dealt with, they have to go out of their way to do it themselves.