H721
Scenario 1
Under normal circumstances I would sign that one off as a non-airworthiness item. (In my company MEL Ref 05-01)
Except if it is a -400 series with vacuum toilets, in which case you need the water for toilet flushing. MEL Section 38 should sort the men from the boys on that one.
Scenario 2
The question that a certifying engineer (and a/c commander) has to ask is..WHY will the door not disarm from the outside? It maybe a symptom of a more serious problem!
I'll stick with the philosophy...If it aint in the MEL I do not sign it off.
If a Captain wants to take the a/c with an open entry in the book then that's his look out! (and more paperwork for me filling out CHIRP and MOR forms!!

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Good topic, well done all for keeping it professional without the sniping often seen on PPRUNE.