1. Do blocks stop the night kill?
2. Does the NK block other actions? (Not needed for spy--so really, can the doctor self-save?)
3. Do the baddies get a NK after the first baddie gets his role?
4. Does the first baddie learn the id of the second baddie if only the first has solved the puzzle?
If yes to 3, but no to 4, the baddie might end up killing his partner.
Balance? It really depends on the difficulty of the puzzles.
5. Are all .zip files protected by the same password/puzzle?