Something I would love to see big finish do, is adapt some of the unmade Sarah Jane Adventures' stories in the style of the Companion or new Doctor Chronicles. With a Narrator, possibly Anjli Mohindra or Sadie Miller, filling in for Liz sladen with other cast members reprising their roles. some of the stories I would most like them to make would be the sones with Ace, the 4th Doctor and Meet Mr Smith. Midnight would also be a good choice as it focuses on Clyde and Rank so Sarah doesn't need to be in it, could be a good weeping Angel story. Sarah Jane vs The Doctor, though with another Doctor other than Smith, most likely Colin Baker since he's usually the Doctor who appears in spin off material.
"it's seems that I am some kind of a galactic yo yo" - Jon Pertwee, The Claws of Axos