I think they just took some of those plot lines and decided to draw them out over the trilogy, since they couldnt fit them all in one.
For instance, that Faithful Bride imagery from the pub... chained hands? AKA, this movie does not support marriage, but sees it as slavery/being tied down. Swans are birds, not meant to be tied down. In this script, Liz and Will share a kiss but they make no mention of a marriage. And that idea is shot down in 2 as well.
The idea of Jack turning around and saving Will and Liz... very apparent in 2. Barbossa's line about Liz stealing Jack's heart is also mirrored, though more by Davy Jones and Tia.
Liz is also seen more as a woman in this version of the script. Many lines in which they refer to her as a woman are changed to girl in the movie "the girls blood didnt work, did it?" that sort of thing. They cast Kiera younger than they thought they would cast someone. But she has aged between 1 and 2, and now they are able to incorporate a more womanly aspect of her.
And even in THIS script, Jack and Liz have ALL the chemistry, while Liz and WIll STILL Have none... 😄