Number 2 said that he was a good man, that he is a good man, but if they get Number 2 he will be better. Well as far as I can see, Number 6 was always the better man, judging by the number of 2's he's been able to get the better of during his time in The Village.
Number 2 in 'Arrival' said that the Prisoner may be offered a position of authority, might that position be of Number 2? Perhaps 'Free For All' was a test of Number 6's ability to manipulate such a community as The Village. Of course it was a test that Number 6 failed, because he could not force his will on the people.
'Once Upon A Time' was originally to have been the final episode of the first series of 'the Prisoner.' If they had managed to get Number 6 because he will be better, then if there had been a second series of 'the Prisoner,' it could have begun with Number 6 as the new Number 2. Well how long do you imagine a television series could run with the storyline of a Prisoner maintaining his resistance to The Village? Something would have to eventually give. Either the resistance of the Prisoner would have to be worn down so much that he eventually gave into the coercion used against him. Or the second series would have had to have evolved into something else, perhaps with Number 6 becoming the aggressor against a new prisoner who thought that his life was his own!
Be seeing you