'Perhaps this is too much for a blunt instrument to understand...'
Is it just me, or does M say the phrase 'blunt instrument' as though it's in quotes? As though it has been used before? But it hasn't, in the films. It is, of course, as well all know, Fleming's description of James Bond: "a blunt instrument wielded by a government department". Seeing as M heads that department, it seems a little odd, doesn't it? She's wielding him. 
So this got me thinking... about codename theory. Is it not simply, and quite brilliantly, that this 'new' Bond, this 'rookie' Bond, has actually *replaced* all the ones we saw before? Ie this M is the same M who was BrosnanBond's boss in the last film. But now BrosnanBond has retired, and he has been replaced... by Ian Fleming's James Bond. Hence, slightly sardonically:
'Perhaps this is too much for a 'blunt instrument' to understand...'
A codename theory we can live with? Which explains Judi Dench's presence in the timeline? 
Or not?
Works for me.
Note, though, that Craig's Bond says "I wouldn't dream of it" at one point (when Vesper implores him not to go back to the game), and he says it in a very Brosnanesque way - the Brosmeister says the same words to Q in GOLDENEYE when told that he doesn't have a licence to break the traffic laws.
Could CASINO ROYALE be a straight sequel to DIE ANOTHER DAY? Given that Craig looks considerably older than he really is, it would be possible to view him as Brosnan's Bond, and the Bond of GOLDENEYE - DIE ANOTHER DAY has seemingly yet to meet Felix Leiter. 9/11 is referred to in both DAD and CR, anchoring both films in the same "timeline".
There's nothing to say that the B&W PTS of CR necessarily occurs just a few weeks or months before the main body of the film - who's to say that it isn't supposed to be set
years earlier? Indeed, the black and white photography surely speaks of the distant, rather than recent, past. The Prague setting suggests the Cold War era.
Now, we know from the GOLDENEYE PTS that Bond has been a Double-O since at least the mid-'80s, which admittedly renders M's "too early to promote you" line a little bizarre (I mean, if he's been a Double-O for almost 20 years!), but it may be that M is still bristling over how rapidly Bond was moved up the ladder "back in the day". It's true that Bond mentions the short life expectancy of Double-Os, but it could be that he's doing so mockingly, drawing attention to his remarkable prowess and amazing achievement in having survived for so long against all expectations.
But, yes, I think the codename theory works well enough, and I imagine that quite a few "casual cinemagoers" will have walked out of CR assuming "James Bond" to be a secret service identity. Or perhaps Craig's character just happens also to be named James Bond - weirder coincidences have happened.
