I am pretty sure most cannon symbols are restricted to that character.
Per the CRL: Canon/legends Symbols/Sigils: Canon/legends symbols/sigils are allowed if they are not directly linked to a face character or unique group of characters in the Star Wars universe.
As that is directly linked to Thrawn (a face character) and his group, I don't think it would be approved. You can run it by the app team in the Q & A or ask your local Ruus'alor Sol'yc for confirmation one way or the other.