Jesus said the rich man wanted to have a drop of water placed on his tongue. Just for your information, the tongue is part of the human body.
As for your theory about Gehenna and Hell, you said that the fires of Gehenna were perpetual due to the constant dumping of trash into the pit. And what exactly do you think the souls of the damned are, if not trash? In any case, God can keep fires going without any external cause, just as He did with the burning bush and Moses. Hell is indeed a place. Many Saints and visionaries have been allowed to see Hell by God. Fatima, fully 'worthy of belief' by the faithful, is but one example where the visionaries saw hideous monster-like beings, (humans deformed by their sin), being physically tossed to and fro in the raging inferno. Finally, if the Council of Trent, the most definitive Council of all time, declares that Hell is PLACE of physical as well as spiritual suffering, no Pope's personal little catechism can abbrogate that infallible Council.
So in your theory here, the Rich Man was already raised from the dead and condemned to hell in his body prior to the general resurrection? Just curious.
In any case, God can keep fires going without any external cause, just as He did with the burning bush and Moses.
See, now you are getting closer! The flame in the burning bush was a manifestation of God.
And there is no external cause of the fires of hell, because hell is not a place full of externally stoked flames and heat. The fires of hell is the fire of Almighty God. It warms the saints and burns the sinners. "Our God is a consuming fire." (Hebrews 12.29)
Hell is a sinner in the presence of God.
Without grace after death, a human being becomes a torch.
"If any one abide not in me, he shall be cast forth as a branch, and shall wither, and they shall gather him up, and cast him into the fire, and he burneth." (St. John 15.6) "If any man shall adore the beast and his image ... He also shall drink of the wine of the wrath of God, which is mingled with pure wine in the cup of his wrath, and shall be tormented with fire and brimstone in the sight of the holy angels, and in the sight of the Lamb." (Apocalypse of St. John 14.9)
The "pure wine" is the light behold with the "lumen gloria" of Psalm 35.10 and Apocalypse 21.23 which enables a person to see God. The wine of the wrath of God is the result of a human without "lumen gloria" beholding the vision of God - the vision itself destroys them in corporeal fire, tormenting the soul spiritually AND physically, and the body physically.
Many Saints and visionaries have been allowed to see Hell by God.
They've also "seen" Angels with wings (e.g., Isaiah 6.2). But we know Angels do not have bodies, so they also do not have wings, correct?
A vision is a means given by God to promote understanding, not necessarily the actual reality of the object.