Of the options you mention, the only one that would seem to irreversibly put an end to a wizard is the Dementor’s Kiss. Now consider this passage from Chapter Twelve of Prisoner of Azkaban:
“They call it the Dementor’s Kiss,” said Lupin, with a slightly twisted smile. “It’s what dementors do to those they wish to destroy utterly. I suppose there must be some kind of mouth under there, because they clamp their jaws upon the mouth of the victim and — and suck out his soul.”
Harry accidentally spat out a bit of butterbeer.
”What — they kill — ?” “Oh no,” said Lupin.
“Much worse than that. You can exist without your soul, you know, as long as your brain and heart are still working. But you’ll have no sense of self anymore, no memory, no... anything. There’s no chance at all of recovery. You’ll just — exist. As an empty shell. And your soul is gone forever... lost.”
Lupin drank a little more butterbeer, then said, “It’s the fate that awaits Sirius Black. It was in the Daily Prophet this morning. The Ministry have given the dementors permission to perform it if they find him.”
Harry sat stunned for a moment at the idea of someone having their soul sucked out through their mouth. But then he thought of Black.
“He deserves it,” he said suddenly.
“You think so?” said Lupin lightly. “Do you really think anyone deserves that?”
“Yes,” said Harry defiantly. “For... for some things...”
Here Lupin suggests that the Dementor’s Kiss is a fate too terrible for anyone, even someone who (at the time he believed) was a mass murderer and traitor to his best friend. It is certainly conceivable that this would apply to Voldemort as well.
Note also that Lupin does not have a problem killing bad guys if it comes to it. Take this passage in Chapter Five of Deathly Hallows:
Lupin looked aghast.
“Harry, the time for Disarming is past! These people are trying to capture and kill you! At least Stun if you aren’t prepared to kill!”
Dumbledore, on the other hand, avoids killing bad guys (even though those bad guys sometimes kill good guys on a future occasion).
For instance, this passage In Chapter Thirty-Five of Deathly Hallows:
“Master of death, Harry, master of Death! Was I better, ultimately, than Voldemort?”
“Of course you were,” said Harry. “Of course — how can you ask that? You never killed if you could avoid it!”
Thus, if Lupin who is willing to kill still thinks that no one deserves the Dementor’s Kiss, it is certainly reasonable to suppose that Dumbledore who is not willing to kill would also oppose the Dementor’s Kiss.
Furthermore, throughout the series we see that Dumbledore does not approve of dementors. As one example, we have this passage in Chapter Thirty of Goblet of Fire:
“Crouch is going to let him out,” Moody breathed quietly to Dumbledore. “He’s done a deal with him. Took me six months to track him down, and Crouch is going to let him go if he’s got enough new names. Let’s hear his information, I say, and throw him straight back to the dementors.”
Dumbledore made a small noise of dissent through his long, crooked nose.
“Ah, I was forgetting... you don’t like the dementors, do you, Albus?” said Moody with a sardonic smile.
“No,” said Dumbledore calmly, “I’m afraid I don’t. I have long felt the Ministry is wrong to ally itself with such creatures.”
“But for filth like this...” Moody said softly.
Here we see that Dumbledore thinks that dementors shouldn’t be used at all, let alone the Dementor’s Kiss, even for convicted Death Eaters.
Besides for the above argument, there are also practical considerations. As early as Chapter Thirty-Six of Goblet of Fire Dumbledore was predicting that they would lose the loyalty of the dementors:
“The rest of us sleep less soundly in our beds, Cornelius, knowing that you have put Lord Voldemort’s most dangerous supporters in the care of creatures who will join him the instant he asks them!” said Dumbledore. “They will not remain loyal to you, Fudge! Voldemort can offer them much more scope for their powers and their pleasures than you can! With the dementors behind him, and his old supporters returned to him, you will be hard-pressed to stop him regaining the sort of power he had thirteen years ago!”
By Chapter Eight of Order of the Phoenix he was suggesting that this might have already occurred:
“If it is true that the dementors are taking orders only from the Ministry of Magic, and it is also true that two dementors attacked Harry and his cousin a week ago, then it follows logically that somebody at the Ministry might have ordered the attacks,” said Dumbledore politely. “Of course, these particular dementors may have been outside Ministry control —”
And by Chapter One of Half-Blood Prince the Ministry already admitted this:
“I thought dementors guard the prisoners in Azkaban,” he said cautiously.
“They did,” said Fudge wearily. “But not anymore. They’ve deserted the prison and joined He-Who-Must-Not-Be-Named. I won’t pretend that wasn’t a blow.”
Thus, while Dumbledore might not have been able to predict the exact unfolding of events after his death, he would certainly have been well aware that Harry would probably not be in a position to have Voldemort subjected to the Dementor’s Kiss.
Finally, we should consider whether Horcruxes themselves might protect against the Dementor’s Kiss. Given that Dementor’s Kisses and Horcruxes seem to each be quite rare on their own, it wouldn’t be surprising if a Dementor’s Kiss had never been performed on someone with Horcruxes. As it is, it doesn’t seem that much is known about the Dementor’s Kiss — witness Lupin’s remarks quoted above where he supposes that they have some kind of mouth. While he does claim to not be an expert on dementors, as a Defense Against the Dark Arts teacher we would expect his knowledge of dementors to be relatively proficient.
Given that Horcruxes safely house portions of one’s soul outside the body, it is not unreasonable to suspect that one could be restored in some form after a dementor removes the piece of soul housed in the body. Thus, we could suggest that Dumbledore (and Harry) either didn’t know how a Dementor’s kiss would interact with Horcruxes, or they knew that it wouldn’t work.
