I've noticed sometimes a joint episode can cause the list to appear incomplete. Like if a series has a joint episode or two, it can appear that a few episodes have been missed from a series. So I have an idea I'd like you to consider:
1. While adding an episode you have an option to select it as a joint episode. For example you add episode 1 and select this.
2. When the episode you made has been added, another episode (2 in this case) is created also. Episode 2 will only inherit such things like group, quality and stats, but will not have a file size.(too keep the total size accurate.
I hope I'm not repeating someone elses request or idea.
Joint episode system [OLDREQ]
Moderator: AniDB
See Shadow Files Progress - that's a more complex, yet also a more complete solution for files that belong to multiple eps (or multiple parts/files forming one ep).