I was watching this show for the first time in a long time on Hulu, and just watched the episode where Sam was Al.
Spoiler Alert: So, to save Al’s life, Sam is sent back and leaps into Al. Al walks out of the time travel device holding his head.
Question: Why couldn’t they send back the next person that Sam leaps in to and have him come home?
IIRC, because Sam can’t come home. When he’s set right what went wrong, it’s implied God bounces him to another person.
Right. So leap the person into Sam before he sets right what once went wrong. It is also implied (stated?) in the show that if Sam does not complete his mission, he will not leap and stay forever as the other person. Leap the person then.
If the series had dispensed with all the sci-fi time-travel stuff and intermittent lip-service to theoretical physics and just decided that Sam was a time-travelling angel who had to right wrongs through recent American history in order to earn his place in heaven (and Al was his angel adviser, invisible to everyone but Sam, and babies, and dogs…), it would have been the exact same show.
Thats basically murder.
I don’t know that I agree with the premise of Ultravire’s loophole, but how would that be murder?
The person goes back into their body when what was wrong is now right, it’s just that it didn’t get fixed, and so the person is probably no worse off than they were before* sam took possession of their body.
*“before” is a word that has imprecise meaning in a time travel story.
Sam’s mind doesn’t leap into the other person’s body in the past. His physical self trades places in time with the other person, who shows up in Quantum Leap’s present and spends his time there in the waiting room. Send him back to his own time, Sam comes home, and nobody dies.
Sure it does, this is how Sam-as-amputee is able to freak out that guy by standing up on nonexistent legs. We see Sam as Sam but everyone else sees the body Sam is in, as does Sam when he looks in a mirror.
That’s right. That’s because he is there physically as Sam, not as Sam’s mind inhabiting the amputee’s body.
Sam also leapt into a blind concert pianist, yet still kept his sight. (He was already an accomplished pianist, that’s how he was able to play.)
He leapt into a chimpanzee, but was still able to talk to Al and to write a note. He also dove into water and saved a man from drowning. These were things he could only do as himself, as these things are impossible for a chimp to do. If it were Sam’s mind in the chimp’s brain, he’d be hindered by the physical limitations of a chimp’s brain compared to a human’s, and chimps are physically incapable of swimming.
He impregnated a woman in the past, who gave birth to Sam’s biological daughter, Sammi Jo, who carried Sam’s actual DNA.
All of that is proof that Sam’s physical body is doing the leaping.
Odd that nobody noticed how a three-foot chimpanzee suddenly had the reach of a six-foot human.
So why does he see someone else when he looks in a mirror?
And what of the “Swiss cheese” effect mentioned in the first episode?
Because that’s the way it works. In the episode where he leaped into a Death row inmate, he would have actually died if he hadn’t figured out what he needed to do.
Or a Hispanic inmate on Death Row suddenly became some white dude. 
that was an early trope of " he cant remember anything about himself except 1 when al reminds him and 2 the plot needed him to remember it… also it was sort of an excuse of why he needed al in the first place
God, Time, or whoever is causing him to leap.