I have thought about this before, and it is really hard to do. For me, if I were to maximize and 80-minute single disk format, my playlist would focus more on the music than the story, as my list below is VERY Act 1 heavy and creates a major gap in the story from Act 2. But it keeps all the songs I like the most, and includes a couple of songs that I think most others would say are "must-have" songs that I would maybe otherwise leave off if it were up to me. Here is that list:
1. Dystopian Overture - 4:50
2. The Gift of Music - 4:00
3. The Answer - 1:52
4. A Better Life - 4:39
5. Lord Nefaryus - 3:28
6. A Savior in the Square - 4:13
7. When Your Time Has Come - 4:19
8. Three Days - 3:44
9. Ravenskill - 6:01
10. Chosen - 4:19
11. A Tempting Offer - 4:19
12. The X Aspect - 4:13
13. A New Beginning - 7:40
14. 2285 Entr-acte - 2:20
15. Moment of Betrayal - 6:11
16. Our New World - 4:12
17: Astonishing - 5:51
Total running time: 76:24
This could easily be shorted up if you took out the two instrumentals and The Answer (which is probably the weakest non-instrumental track on the list, in my opinion), which would make room for another 1-2 songs. Those are in because:
-Overture is a nice intro that sets up the album and introduces the themes. It is just a nice way to get started.
-The Answer is a nice transition piece between TGOM and ABL, and it is short and doesn't take up much time.
-Moment of Betrayal is a pretty good song in and of itself. But having that quiet piano intro, and then the strings, and then the full instrumental explosion coming immediately AFTER 2285 really makes it sound epic. And 2285 is really a neat revisiting of the musical themes from Act 1.
If I were going to make a similar list that made the story make sense a bit more, I would remove A New Beginning and add My Last Farewell and Hymn.
If I were going to just make a shorter, more concise playlist that brought it down to about an hour, I would go back to my original and remove Three Days, A New Beginning, 2285, and Astonishing.