I'm in the middle of working out something similar myself right now.
As far as having this play in order. If you do not select random, a fill will choose items *in order* from a playlist. So you can easily have a playlist for the show, or a separate playlist for each portion of the show. I'm doing it where a one hour show will have 4 segments. A playlist for each segment. Items in the order they play. Each segment is required to be approximately 12.5 minutes long, but can vary from 10 to 15 minutes, provided the total comes out to 50 minutes.
For each fill, I'm careful to set the minimum time to where it exceeds the expected end time of that segment, and to have random off, and unique items on. In this way, it will grab each item from the playlist in order, and use them all up without repeating any of them.
The schedule for this hour puts some of my things in around these segments. It ends up something like this:
fill to top of hour in case there is a shortfall
top of hour tone
announcements or news
spot (for an ad)
pick for a show intro theme ( I don't put this in with the show segments. a time saver )
fill show segment 1 (this contains voice tracks and music, or whatever, last voice track mentions the break)
pick or spot here for an ad or whatever. I could put a few picks/spots in a row if needed.
fill show segment 2 (as before, this segments contains voicetracks/music, whatever)
pick or spot
fill show segment 3
pick or spot
fill show segment 4 ( the last voice track in this one closes the show )
pick for a show closer theme (again, I don't have this part of the show segments )
In my case, I'm doing this because someone out of studio is preparing these show segments. I have them order them properly, and put the episode number and segment number in the comments. They burn this to a CD and give it to me. I import the CD in to the stations itunes, add the segments to the show segments playlists, and it's ready to roll.
I also have them give me a print out of the order for me to check against, in case of problems.
My tests of this are working out so far. I need to look at seeing if I can stack up a month worth of shows, or even a whole season of shows in advance. As it is, I can have several weeks imported in advance, and merely need to add each show to the playlist manually in advance each week. Not too much work, but forgetting would mean a repeat. If I could fully automate an entire season, that would be swell. I haven't figured out a way within iTunes/Scheduler, but it's possible I could write an applescript routine that would cycle them for me automatically. I may yet look into that.
Actually, I already have an applescript routine I could use, now that I think about it. I control community announcements through such a script. I put a date range into the grouping field, and run a script nightly that checks the range, and add or removes the word 'valid' to/from the tracks. So I could make a smart list that checks for valid, and for the segment number in the comments, and adds those tracks to the right show segment.
I'm pretty sure I've posted that script on this site, if you want it.
Long winded, but i hope it was useful.