Duncan,
You wrote "An act, or sign, unmistakeably originating from God, would profoundly affect the way people view things. There may even be, for all I know, a dedicated hard-core percentage of humankind determined to oppose him, but surely that would be a vanishingly small minority. Most reasonable people would unfailingly want to be on the side of God. Once they knew, unmistakeably, what side that was."
Not certain about that. Few thoughts...
First of all, what sort of sign? Take Jesus. In the Bible I think only 4 people ever raised someone from the dead. Granted, one of them was a pile of bones (Elijah/Elisha?), Jesus, and Peter. What if TODAY, you saw someone raise someone from the DEAD? Real death. Lazarus decomposing in shroud type death. Would you belive? If so, why dont you believe now because Jesus already did that (allegedly). Now I wasnt there personally, but the account can either be true (fact) or false (lie, fable). But not both. Someone asked an interesting question thread regarding whether Satan can create life. If he can, and I was him, I would do it just to divert and confuse humans. If he cant because God "governs" life force authority, why dont you believe already? Why do you need another sign? Another problem is in other "holy" works there are similar stories. Like Pilate said, "What is Truth?"
Second of all how could you know the sign maker was God? See Satan vs Job. Jobs wife thought it was a sign from God. Even Job wasnt too sure. The least of the angels is far, far beyond man. Yet no so far above as to take on bodies and have sex with women. Hmm. Anyway, their power would seem 'godlike' But reduce the scale. Say, you were a gunsmith with machinist insight and could craft bullets and machine guns of today back in Israels time. Might not need those drums at Jericho.
Third point is I think there is something in man that resists, call it what you will, but I call it gods civilization. I find professional boxing a case in point. To me it is compelling not for the athletic spectacle but rather to observe the crowd. Men, women, all races, all ages, religions, etc react, cheer, for two men to beat each other up. Hopefully to unconsciousness. But if not blood will do. We compete independently. And competition is not always pretty. If not physically, then socially, monetarily, intellectually, in every way imaginable. Distinctions create division. The WTBS many times has referred to the Men of Old coming back to rule as "princes" Moses was an interesting guy, probably worthy of being a prince, but I tell you what, I would never bend my knee to him. That sentiment alone is probably a death sentence. I recall when I was about 16 an Elder gave a talk regarding the "New Order" where they would "learn war no more" and then drew a parallel to some kid playing violent video games learning war. Do you really want to live in a world where the only video games are on needlpoint? Or have someone else dictate/determine what you do in life?
"Brother Duncan you are going to be a construction worker for the time being. Start bulldozing those bodies in a mass grave, while I a "prince" pick out my mansion like property, I mean my humble abode. Fear not! This is Gods arrangement" Does that sit well with you? Even IF that is Gods arrangement?
Finally, why would you want to be on gods side? To live? Because he is "right"? Or it is our destiny because he is the "Creator"? OR is it because he is the most powerful and could protect/give us what he/you thought we needed/wanted without all this hassle we call "life". Bills, $$$, crime, pollution, etc.
Doleing out signs, life, items, in exchange for behavior and loyalty is bribery. You should serve your god because you want to and you find your life better for it. But read that sentence again. Isnt that self serving anyway? Pretty much.