Under-Henge Six figure set

[judooning]

And Vastra would be a tweak of Alaya and Restac.

So all in all, it would be a fairly good set on CO's side. And they could re-released dorium witout a head. So that leaves Madame kovorian and a headless monk that would be totally new figures. I'm sure CO would love that

[Hellbelly]

And Vastra would be a tweak of Alaya and Restac.

Fairly substantial tweaks though. Really you'd only be re-using the head (and maybe the arms).
I don't see CO releasing 4 new figures in a mass market set, not for £30-40 anyway.
I'd think it would be more likely we'd see something like;

12th Legion Cyberman (or better still Cyberleader)
Strax
Judoon Trooper
Silurian Warrior
Headless Monk with removable hood (variant of carded figure if it's released)
Dorium (exclusive to this set, at least for a while)

And what if the Headless Monk comes with an 11th Doctor swappable head for a "Eleventh Doctor in Monk disguise" figure?

[Rosetyler]

You'd most probably get....

Doctor (A Good Man Goes To War)
Sontaran
Madame Vastra (HIGH MODIFICATION)
Dorium (Possibly)
Judoon Trooper
River (Possibly) or A monk

IF YOU WERE EXTREMELY LUCKY RORY OR KOVARIAN.