Fair enough. In such a world, that would certainly do the trick.
But let's refine the quest a bit, and look for a God that chooses to not act in that manner. After all, such a thing has yet to happen, so if God DOES exist, our wishing for such a thing will not help us in our search for God, will it?
So, in the absence of a God that would be willing to do an en masse conversion of humanity, how do we prove the God that actually exists?
Put another way, I want to know how we could know for certain the God that actually exists, consistent with our present reality; not the God we wish we had, of a different reality.
I happen to think it's important to be pragmatic concerning questions like this and to realize just what our limitations as human beings actually are. Obviously this question in particular will not reach the level of consensus as to what it's like getting wet brings, or getting burned by an open flame is.
We may be able to divulge further in some manner and perhaps reveal more than we know now, yet there is no true determination to be had as this stands. Like you mentioned simply wishing for it doesn't settle things. Ironically enough if one notices well, the entire and direct truth of this matter lies all around and within you, but due to our limited nature there is no intellectual grasping in spite of directness of it all. Yet there it is, all the same. Real truth (AKA God) being present this very moment. Shake hands now.
To me, this is actually God met face to face already long introduced and well acquainted. Personifying this further or not as God, I would think would be a persons own choice as such direct realities at present need no argument or debate. I would think the arguments are really over the bad habit of personifying the direct truth of which this in turn is given various characteristics and attributed events in time giving way to various religions without realising the manipulation of it all making things confusing.
We as human beings can actually settle the issue of God one and for all, but not towards the manipulation brought about by habitual personification that so many people happen to cling to of which I view as "God".
To prove that God (or "God") exists, all you have to do is directly experience the obvious and just leave it as being such. That's how I now go about all matters of proof by simply stating that theists as well as non-theists happen to be dealing with one obvious direct truth using their own particular ways of which neither side being right or wrong in way of describing the effects because the real truth of all things remains steadfast, no matter what we say, claim, or discover about it.