Oh, Bond does not actually need a character arc; as you said, there are plenty of solid Bond films with no such thing. Neither do I think Bond absolutely has to avoid every form of transformation or ‘growth’ - and still remain Bond. Seeing him throw his gun away and driving off is perhaps the best example. And few would argue that’s no longer Bond collecting the Aston.
What I mean is, if there are such groundbreaking developments in Bond’s world as indicated in SKYFALL then they ought to be addressed in some form by the - nominally - centre character. But that’s never happening, perhaps to avoid too much conflict in an already conflicted tale.
Instead we are presented with backstory for Moneypenny and even some for Mallory - and when did we ever need that? All of it is logic to some extent, meaning if they were real characters in a real world they’d possibly have similar backgrounds and act in much the same manner.
Meanwhile Bond’s actions are simply driven by unwavering loyalty. But that’s what we expect of him anyway. What we are not shown is why he’s so faultlessly loyal in view of everything unfolding in front of him.
We can of course guess, we know of course (this) Bond’s entire career under (this) M’s command. But it’s still curiously uneven to see Bond drop out at the start of the film, without much reason - only to come back and not be affected by events until the very end. M’s death has some impact, true. The images have enormous impact, also true. And here I’m not sure whether the images (also his own image) carry not more import than everything we’ve seen during the two previous hours.
He’s standing atop the roof looking across Whitehall, an iconic view and Bond a part of it, like a stripe on the Union flag. And the whole pomp and circumstance is even nicely broken by the pot-ugly bulldog, ironic and playing to the sentiments of the audience. Maybe this is all the character arc for Bond in SKYFALL, from standing without much reason or explanation in a Visit London Now! ad to the moment he’s facing M - now at codename terms.