Sometimes it's easier to just redownload in a format that's more usabe than trying to make do with what you got. Obviously there's a bunch of reasons why redownloading could not be a valid option.

If there's only one intro per season, selecting a member at random from a set of one means it picks that member.

You could also add the intro to the videos. It should be trivial with ffmpeg or any other video editor.

Okay, that's a pretty cool request. But how much space does it actually save to do it like this?

You could try the trailers sub folder?

Look up ordered chapters