Option to Disable Arming if Sensor is Open

That would be "fail dangerous" instead of "fail safe".  Not sure that's a useful feature.  When you ask it to arm, why would you want it to not arm?  Versus warning you about open sensors and arming anyway?

If that open sensor gets closed after arming has been initiated, it becomes active too.  If it doesn't get closed it just stays bypassed.

Even if that open entry sensor allows a bad guy to enter my house, other sensors of my armed alarm will catch him and set the alarm off.  If the alarm remains unarmed, I would have zero defense.

Just to play devils advocate what if you had a hungry mob of zombies walking slowly toward your house and you needed to 'somewhat' quickly arm the system, because zombies are dumb, and hate loud noises perhaps.  You hit the home button and sigh in relief, but oh no! Whats this?!?!  The system won't arm because a window is open somewhere.  BUT WHERE??? Now you are faced with finding that open window (again, 'somewhat' quickly) before the hungry mob reaches your house.  Can you outpace them in this race for you life?  CAN YOU??? Remember rule number 1, Cardio!

there no zombies i'm talking about arming the system with all sensors in the closed position

Arming the system with sensors in the open position is not a safe system.  example one morning I'm late for work and running out the door and my wife calls me back , she is not feeling well and will be staying home from work and ask me to feed the dog and arm the system in the home mode but there is on thing i forgot to do is close the back door. I'm in my truck arming the system , wife is home sleeping someone enters the back door the  motion detector is in the off mode. i leave the rest to your imagination. that is what I'm talking about  the system is not safe to arm when  sensors are in the open mode. the system should not arm you must go and close the open sensor please advise

It would be less safe to refuse to arm with an open sensor.  At least every other sensor is active.

If it refuses to arm then either 1) you won't know that it did not arm and you have NO protection, or 2) you have to track down the offending sensor(s) and deal with them, which may take more time than you have.