Why does Lupin not seem to find out about the castle's laser defense systems until he observes Zenigata being given a tour of the castle grounds, considering that he's been inside the castle once already (as he reveals early on to Jigen)? The lasers were installed after he broke in the first time, to prevent a thief like him from breaking in again. Obviously, they fail in that task, since this is Lupin we're talking about.
This film was intended to serve as Miyazaki's vision of what a Lupin IIIGrand Finale would be. This puts things into a different context:
Lupin and Fujiko are both Older and Wiser, and employ more pragmatic tactics: Lupin favors simple tools (seen with the cheap lighter and the Fiat) over gadgets and diverting people rather than outright humiliating them, while Fujiko goes for sneaking around and More Dakka offenses rather than relying on her seduction techniques.
The film indirectly portrays Lupin feeling regret over the life he's lived.
Fujiko not being a femme fatale comes from Miyazaki having made Lupin Lighterand Softer, but also it's a sign that as she gets older, she'll have to rely on her physical beauty and sensuality less.
Zenigata's got a whole squad to lead, probably due to all his hard work finally being recognized and him being promoted.
Fujiko makes off with the counterfeit plates at the end of the film partly to mess with Lupin, but also because she's got her hands on a superb cash source (as long as nobody finds out that her money is unlawful).
In Part 5 Clarisse shelters Lupin there to hide him from PeopleLog. Cagliostro is a small and insignificant country that is the last place anyone would think to look for someone as famous as Lupin III.
Goemon often complains that cars, buildings, and anything inanimate is not worth to have been cut by his sword. As the final showdown starts, he tells Cagliostro Elite Mooks that his sword is about to feel happy. He told them he was going to murder them allbefore the camera moved away. And by the time they surrendered, many of them didn't move anymore...
Did Lupin drown the diver he captured? Was he able to catch the swimmer, render him unconscious, and drag him back to the surface? If so, it's a cruel bit of self-defence.
Fridge Heartwarming
Lupin's return to Cagliostro to initiate his final job in Part 5, he's hiding out in the catacombs where he and Zenigata shared a cigarette together. So seeing the man who rescued her in this much danger must have led Clarisse to give Lupin asylum from PeopleLog, all to save the world once again.
