You cannot rule a dead ball for OBS without changing the philosophy of the rule.
The rule's purpose is to remove the effect of the obstruction. This applies to both sides. IOW, the offense gets to get all they can get
out of the play, but so does the defense, with the caveat that the defense is not allowed to benefit from the obstruction.
There are several situations whereby even after judgment the runner is protected to home, the runner would not score. Example: missed base appeal. Example: interference. Example: malicious misconduct.
If you tried to write the rule to deal with all the situations, it would be a very narrow rule, and the only object would be to prevent possible injury in a very routine softball play.
Not worth it, IMO.