We've had the Bat box set discussion before. I suppose it just shows how popular the album still is that Sony doesn't feel the need to boost sales by putting some effort in.
Anyway, a good box set should feature:
The album, remastered to a higher standard than last time (and remove the click in FCOL before the orchestra kicks in)
A CD of outtakes and alternate edits
A live CD from the start of the Bat 1 tour (My Father's Place or El Mocambo would be good)
A live CD of the Nassau Coliseum show
A DVD featuring the music videos, any interviews and other performances (if such things exist)
I would pay decent money for that lot.