The title pretty much says it all. I used to play regularly with a group of 7 other people. Now we're down to 2 (including me) for one simple reason; frustration over not being able to finish longer quests in a reasonable amount of time.
We all are pretty busy but we set aside 2 hours a week to play, and we all had VIP accounts. Unfortunately, that meant we could often do only a single adventure, and sometimes not even that. While we love the story telling and richness of the long adventures, we just didn't end up playing them, and after awhile the shorter content gets dry (how many times can you do an orchard run?).
If we could save the progress of the party it would totally transform the game for us, and we'd get the rest of the guys back I'm sure. We can't be the only ones who would like this. It would even be awesome for soloing.
Mechanically it could work like this perhaps:
1) When no combat is ensuing, the party leader can initiate a save.
2) Saving logs those characters out. We don't want it to become a "redo", or a way to keep retrying a difficult part of the dungeon.
3) A timer starts on those characters (1 hour? 3 hours?). Until the timer ends they cannot log back in.
4) Some time later the party logs back in.
5) The characters go to some kind of lobby or something until everyone is in, or the party leader re-starts the dungeon.
6) Once restarted characters that don't come back are affected the same way they would be if they left the dungeon; so is the party.
7) New characters can join the party with all the usual consequences of joining late.
8) A player can pull their character out of the saved dungeon any time after the timer ends, but they will not be able to re-join the saved state except as a new joiner.
Anyway, something like that would be huge for us. It would allow people with only a couple hours (or less) at a time to fully enjoy the game.