First off, you can organize the order of the sequence any way you want. So, the order you have chosen may be the one in Witness, or some permutation of it may be more appropriate. Secondly, I've never read the script and it's been a little while since I've seen the movie, but I'll give it a try using the sequence you provided.

• Delay/Choice comes at the very beginning of the movie. Rachel is barely widowed when a local suitor (Daniel) makes it very clear that she is his choice for a wife. She delays the matter by going to visit her sister "among the English." Delay is shown to be advantageous. Choice is not.
• Delay/Preconception seems to come when the police are first introduced to the "witness" and his mother. Rachel is concerned about the delays to their trip, while the police express concerns about certain preconceptions of Amish and children witnesses. This thematic exploration continues on through the roughing up of suspects (preconception of guilty parties), and up to the point John realizes the bad guys are cops (Samuel's choice of perps).
• Delay/Openness starts with a touch of it in the witnesses at John's sister's house segment ("Your sister says..."). It really takes hold during John's early recovery from the gunshot wound while staying amongst the Amish. Rachel uses John's condition to delay her complete withdrawal from the English by bringing him home. The elders show great openness by allowing John to be healed and recuperate at Eli's home.
• Choice/Preconception seems to begin about the time the boy Samuel finds the gun. This brings up issues of choice of life-style and the preconceptions the English have of the Amish, and vice versa. This continues through the discovery of what is and is not permissible amongst the Amish, and discussion of characters' life choices (most particularly John's and Rachel's).
• Choice/Openness comes to the forefront during the barn building sequence. Rachel seems to openly flaunt her clear choice of John over Daniel. Meanwhile, John is more open to the positives of Amish life and both he and Daniel recognize the choices each must make. The Amish women are somewhat scandalized by Rachel's choice AND openness of her preferences.
• Openness/Preconception opens with Eli confronting Rachel about her relationship and her place in his home, and climaxes with John's speech to his boss Chief Schaefer. This scene contrasts the openness of the Amish Society and the exposure of the Chief's wrongdoings to an innocent crowd with the single-minded, preconceived view of the world held by Chief Schaefer (and, to some degree, John Book).

Ultimately, the thematic conflict of Delay vs. Choice is played, rehashed and emphasized in the final scenes. Both John and Rachel realize that the delay has given each of them time to explore the potential opportunities. Rachel chooses to stay among the Amish. John chooses to return to the English. And as John drives away, he passes good ol' Daniel coming to pay a call on his original choice for his wife.

That's a rough guestimate of the OS thematic sequence for Witness. There's a lot of wiggle room when you're talking about thematics, but I hope this gives you some direction for use in your own work.