...the ones who weren't ready when the Bridegroom came...
In the parable of the 10 virgins, some believe the wise virgins must be taken in a pre-trib rapture. But note that the door is closed at Jesus' coming (Matthew 25:10, compare Luke 13:24-28), which Jesus had just finished saying would be "immediately after the tribulation" (Matthew 24:29-31). There's no 3rd coming of Jesus.
I believe Christians will either be ready for Jesus' 2nd coming or they will be lost, as the 5 foolish virgins are lost: "The bridegroom came; and they that were ready went in with him to the marriage: and the door was shut. Afterward came also the other virgins, saying, Lord, Lord, open to us. But he answered and said, Verily I say unto you, I know you not" (Matthew 25:10-12).
"Then said one unto him, Lord, are there few that be saved? And he said unto them. Strive to enter in at the strait gate: for many, I say unto you, will seek to enter in, and shall not be able. When once the master of the house is risen up, and hath shut to the door, and ye begin to stand without, and to knock at the door, saying, Lord, Lord, open unto us; and he shall answer and say unto you, I know you not whence ye are: Then shall ye begin to say, We have eaten and drunk in thy presence, and thou hast taught in our streets. But he shall say, I tell you, I know you not whence ye are; depart from me, all ye workers of iniquity. There shall be weeping and gnashing of teeth, when ye shall see Abraham, and Isaac, and Jacob, and all the prophets, in the kingdom of God, and you yourselves thrust out" (Luke 13:23-28).
"Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity" (Matthew 7:21-23).
...it wasnt the wedding time then...
Note that the Bible doesn't show the marriage of the church or the marriage supper happening before or during the tribulation, or in heaven; it doesn't announce the marriage and supper until the 2nd coming, immediately before we descend with Christ at Armageddon (Revelation 19:7-9, 14).
After the tribulation, I believe the rapture will gather us into the clouds to be married (Revelation 19:7) before Armageddon. The supper will be on the earth after Armageddon (Revelation 19:9, 17; Isaiah 25:5-9).
Note that the supper on the earth in Isaiah 25:5-9 is spoken of in connection with the same coming in which Jesus "will swallow up death in victory" (Isaiah 25:8); "Then shall be brought to pass the saying that is written, Death is swallowed up in victory" (1 Corinthians 15:54).
In the pre-trib view, why isn't the Lamb at the marriage of the Lamb (Revelation 19:7) or the supper of the Lamb (Revelation 19:9) at any time we see him during the tribulation (Revelation 5:6-13; Revelation 6:1; Revelation 7:9-17; Revelation 14:1-4)?
...the ones who are left behind in the rapture...
Regarding "one taken, one left," I believe that in Matthew 24:36-44 Jesus is referring to the same "coming of the Son of man" as when he said "immediately after the tribulation of those days... they shall see the Son of man coming" (Matthew 24:29-30). I don't believe that Jesus taught a 3rd coming. Note that Jesus is speaking to the same believers, the same "ye," in Matthew 24:15 that he is speaking to in Matthew 24:42.
In the pre-trib view, how will "one taken, one left" be a secret pre-trib rapture and not an event at the revelation of Jesus, when "even thus shall it be in the day when the Son of man is revealed... Two men shall be in the field; the one shall be taken, and the other left" (Luke 17:30, 36)?
I believe the ones "taken" at the 2nd coming are unbelievers who are killed, just as Noah's flood "took" evil men away (Matthew 24:39-40). The carcasses of the ones "taken" are eaten by eagles and other birds (Luke 17:36-37, Job 39:30, Matthew 24:28, Revelation 19:21).
I believe the ones "left" at the 2nd coming (Matthew 24:40, Zechariah 14:16) will be survivors of the heathen nations that came against Jerusalem, who will be forced to worship Jesus in the millennium (Zechariah 14:16-18), and whom we will rule "with a rod of iron" during that time (Revelation 2:26-29, 5:9-10, 20:4). They will be the ones who will populate the millennium.
The ones "gathered together" at Jesus' 2nd coming are his elect (2 Thessalonians 2:1, Matthew 24:31). So I believe Christians won't be the ones "taken" or the ones "left," but the ones "gathered together."
...who then believe in Christ (convert)...
Note that it doesn't show anyone repenting during the tribulation, but says that the unbelievers "repented not" (Revelation 9:20-21, 16:9-11), and that at some point in the tribulation "God shall send them strong delusion, that they should believe a lie: That they all might be d*amned who believed not the truth, but had pleasure in unrighteousness" (2 Thessalonians 2:11-12). So it's possible the Christians we see in the tribulation are us, saved before the tribulation began. Jesus doesn't promise us a rapture before the tribulation.
[*The posting program doesn't accept the word d-a-m-n-e-d.]
I believe giving unbelievers the idea of a 2nd chance is dangerous. After hearing the ideas of a pre-trib rapture and a 2nd chance, unbelievers could get complacent and say "Oh, when I see a pre-trib rapture happen then I'll repent and believe; I've got a 2nd chance, right?"
I think instead we should warn them: "The Bible doesn't promise that there will be a rapture before the tribulation. And in the great tribulation God is going to send a strong delusion (2 Thessalonians 2:11) on all those who rejected the gospel. Today is the day of salvation. You may not get another chance to believe."