@digifuzzy: Well, your above proposed solution will make the save file work 
again, but may impact the gameplay, depending on how much the engine was 
modified.

By example, on this case, all 999 wouldn't have their special sensor, as well 
the terminal guards. This is a minor effect that happened, but it could be worse 
depending on how much the C code was changed. A example would be if I renamed 
'max_energy' field to 'max_life' on *enemy struct. We couldn't have a default. 
So we would need, in fact, abort the loading.