Just to pick up on this point here (I agree with the rest of your post), I think the reason Cameron didn't get involved until lastminute.com is that he knew his presence would do more harm to the No campaign than good. In fact, he was very likely advised by the Scottish parties not to put in an appearance or even say much about it.
It is fair to say that an Etonian Tory is about as welcome in Scotland as rabies.
That was certainly his explanation, but given the consequences, he was either incredible naive and arrogant, or simply very badly advised.
They left the entire no campaign in the hands of a failed PM who is generally known, (both rudely and unfairly) as the one eyed Scottish idiot and his chancellor who over saw the UK plunging into what is claimed to be the worst recession since 1928.
Cameron and Miliband both refused to compromise. Cameron was offered so called Devo-max, which he could have negotiated to be attractive, yet maintain stability. He refused point blank.
Instead both he and Miliband simply stayed in London, poking fun at the whole thing, until the last minute almost when the queen ordered them to go.
Its all so incredible, I doubt the historians will believe it.
The UK principals have literally backed themselves into a corner. They can't ignore the Scots, they certainly can't ignore their own partys, and there is so little they can do because they've already promised the Americans they will attend the next ME blood bath.
Anyway, for those who asked, this is why the Scots are keeping the pressure up. Because they know the UK will almost certainly hope they can put this off, entertaining people to a few patriotic victories,perhaps with a few heros giving their lives, ect..
Cameron must be thinking, never were the second verses of God Save the Queen more appropriate than now.