One does not have anything to do with the other. With the meat sacrificed to idols, the focus was on the meat. Nothing about the meat was tainted. The meat was not pagan. There was nothing wrong with the meat. The only action with the meat was you eating it. On your idea of transforming pagan days, you are engaging in tainted rituals and ceremoneies. The focus is on the pagan practices and symbols.If Paul could say through the inspiration of the Spirit, that it is acceptable to eat meat sacrificed to idols, then I can't see how the same Spirit is going to have a problem with transforming a pagan holiday into a celebration of the incarnation.
Your linking of the two situations would work if Paul was saying that one could do something with the idol, which was evil and pagan, BUT IT WAS NOT. When you talk of pagan days somehow being made to pass for a Christian holiday, you are "touching the idol".
Further, you never see anyone in the New Testament Church doing anything similar. Did Paul ever change a pagan day into a Christian day? Did Paul ever use idols for something else? Did Christ ever advocate doing this?
I frankly am not going to do anything Jesus Christ did not advocate. It was He who said that I should live by every word of God (Matthew 4). Why should I live by the traditions of MAN?