Good point. Perhaps it was Barnabas' offer of help that started changing Quentin's personality and outlook. I mean, by the time September 10th rolls around he's been put through so much more via Petofi and the family falling apart than he may have originally been. Perhaps in the "original" he was just as cold and conniving as we saw at the beginning of 1897 before things were really changed. It's certainly more in keeping with the way his ghost acted.
They could have brought David Selby back in 1969 with a blond plastic wig and named him Cassander.
The craziest statements he makes has to be when he accuses Angelique of changing history when she announces that she plans to marry Quentin and she accusaes him of the same. His response was hilarious: "I have done all i can do to make sure to keep histpry the way it was" or something to that effect.