We know that there will be a correcting and refining, that is unavoidable scripturally. The weeping has never given me a problem since we have verses like this, “weeping may endure for a night (outer darkness), but joy comes in the morning”. Gnashing simply represents the stubbornness of the unrepentant, which is the whole reason they are going through judgment in the first place!
I think the whole interpretation of the parable comes down to this passage,
"[The angels] shall gather out of his kingdom all things that offend, and them which do iniquity and shall cast them into a furnace of fire: there shall be weeping and gnashing of teeth. Then shall the righteous shine forth as the sun in the reign of their Father. (Fun little thought: the phrase and them that do iniquity can be translated as and that which causes iniquity)
We know by Scripture that the furnace isn’t evil, in fact why would Jesus say people are thrown into a fiery furnace? Where else in scripture is this theme of people figuratively being put through a furnace?
“As one gathers silver and bronze and iron and lead and tin into a furnace,
to blow the fire on it in order to melt it,
so I will gather you(Israel) in my anger and in my wrath, and I will put you in and melt you. (Ezekiel 22:20)”
(Later in chapter 39 God declares that Israel will be restored, so to be melted in a furnace mustn’t be a final state.)
“Behold, I have refined you, but not as silver;
I have tried you in the furnace of affliction. (Isaiah 48:10)”
“The crucible is for silver,
and the furnace is for gold,
and the LORD tests hearts. (Proverbs 17:3)”
I think my favorite is the Proverb, notice that the furnace is for gold, combining this with the wicked being touch-stoned* in the Lake of Fire (a process which was used to test the value of gold and silver) we begin to discern a clear picture throughout the scriptures. God is putting the wicked into the furnace of fire to touch-stone(test) them like precious metals, only through this process can their true value be found. The final result is “Then shall the righteous shine forth as the sun in the reign of their Father”, realizing that all people are children of God (Acts 17), then we see this as a prophecy about the wicked’s final redemption and not of their eternal punishment. Remember the reign of Heaven is within, it is something that God must establish in every heart, by this testing in the furnace of affliction the war is won and the kingdom established.
P.S. If anyone thinks this interpretation lightens the impact of the cross and the blood of Christ, I wish to draw their attention to the very plausible interpretation of the ‘Lake of Fire’ as the blood of Christ burning away all sins. The Revelation is just that, an uncovering of Jesus Christ, its about him and his work. The Fire purifies and touch-stones everything, for everyone will be purified with fire.
*Touch-stone is translated as ‘torment’ in most bibles, however the Greek word here is ‘basanos’ and it literally is a black stone used for testing precious metals. To translate it as torment is a stretch, ‘testing’ is a better one.