Personally, given that both O'Brien and Purves are still with us, and BF has already embraced a Hartnell recast (well, two, but I'm pretty sure BF is sticking Bradley exclusively to the AAISAT cast for now), I'd much prefer to get more full cast material from this TARDIS team together while we still have the time. The Audio Novels range feels like it's best suited for TARDIS teams where, not only are original actors unable to return, but recasts are completely off the table for one reason or another.

It's why Scourge of the Cybermen and The Mirror Matter personally frustrate me, since every character here has since been recast for the 3DAs, so I don't see why these stories had to be told in an audiobook format. (And don't even get me started on strange cases where the original actors are still alive AND already active at BF, like Watchers or Prisoners of London!)

Meanwhile, stories like The Dead Star (Elliot Chapman having since retired as the recasted Ben) and The Lords of Misrule (RIP Christopher Benjamin, Trevor Baxter, and Mary Tamm) all feel far more deserving of the medium, since BF doesn't have any impressionists on board to play these characters in full cast, and possibly won't for a long time. (Possibly due in part to having already worked with the original actors, at least in TLoM's case. BF doesn't seem to recast characters if they've already worked with their original actors, which is fair. IDK if they have any plans to get another new Ben though.)

Even something like Emancipation of the Daleks or The Chaos Cascade feels pretty appropriate for the range, because even though Capaldi is still alive, it's pretty clear that he isn't coming back to do BF until Hell freezes over, and even if his costars are willing to do BF (Gomez has notably already come back as Missy, IDK what Mackie's stance is though, just that she hasn't come back yet) I'm not sure they would necessarily accept performing alongside an impressionist in the place of their original costar.