Literally anything.
Cryomancer is so basic, you really only get F12(2) (You lose the HKD from F12), F42 Grab (you also lose the side switch ender), and a hammer...
All that should be in his core design, it would be the equivalent of Kung Jin having a variation called "Cartwheel" in which it gives him his Cartwheel move, except it comes at the expense of something vital his main variation...or Tanya having a variation in which she gets her Low Drill and Overhead Flip kick...
But specifically:
Regular hammer should push the opponent way back on block, while MB hammer stays as is.
Hammer should block string from more strings, such as 111, F42, 12, B33 etc.
MB Air hammer should launch, and should block OH then LOW.
D2 should be faster.
NJP should include the sword.
111 should be +2
None of these are buffs, they are how the moves should work.
Also, I don't see why F424+2 isn't an actual Grab that the opponent has to jump out of crouch or armour on block...
Other than that, they might do something like Hammer cancels or something, but it won't really help him unless they are plus.
Both Unbreakable and Cryomancer need a total overhaul, both are terrible.