How would you Write the Kett out of the series?

That was my assumption, but it is possible he survived.  I'm not sure about being forced to recreate the motions but they did display the ability to hack memories so I could see that.  Maybe he was mostly dead and cold only get recent memories or something.  Its also possible exaltation was the only thing that could save him.

So I'm trying to picture what happened.  Your dad is lying right next to you.  You see the rescue ship right over you as you're passing out.  This ship lands and rescues you, but is unable to tell that Alec is still alive, and then just leaves the body there and takes off.

Then, show me the frame where you're clearly seeing the rescue ship right over you.  We're told the ETA is 4 minutes and that scene in it's entirety is no where near 4 minutes long.  Personally, I'm not seeing any ship at all behind dad's head before Ryder first passes out.  Young Ryder regains some consciousness afterwards as the shuttle gets there, loses it again, regains it again for a bit, etc.  Each time he/she passes out, time skips ahead and we don't know how long the skip represents.  We're told that somewhere in there he/she is dead for 22 seconds, but the point of death isn't even very clear.

If Ryder is passed out for, say 3 mins and dead for 22 seconds of that 4 minute ETA for the shuttle, that's plenty of time for the Kett to come and take dad without Ryder even knowing it.  Why not take Ryder too... well, if the Kett believe he/she is dead, they might just decide to leave him/her for dead.  It was pointed out on another thread way back that N7's are trained to hold their breath for long periods.  Also, the first time SAM killed and revived Ryder to save his/her life may have been on H7.

Not necessarily.  They may have searched and found nothing and presumed him to have died - fallen into the abyss below the monolith.  If they wanted it to be absolutely clear to us that Alec died, why didn't they just show a body lying next to Ryder in the shuttle on the way back to base or a body being taken away (to the morgue) on a different stretcher or even have Cora say "We recovered his body.  He didn't make it."?  With 2 hours to grieve, why doesn't Lexi say something like "If you want to spend some time saying goodbye, your dad's body is in the morgue."?

Whatever floats your headcanon is fine with me too... but just realize you're actually making assumptions just as much as I am.  Bioware hasn't made anything absolutely rock solid here... and they've probably done that intentionally.

MIA can also be MIA - Presumed dead.  Maybe transferring SAM out damages said implant.  We can both speculate all day long here.  You're assuming just as much as I am, so stop behaving like all the facts are irrefutably there.  You can believe your own headcanon.  I've said before that it's my theory and it makes the story more interesting for me.  My privilege given the vagueness written into the story and what, allegedly RPGs are all about.  If I want to play a story that can only be interpreted one way, I'll play an action/adventure campaign.

Alec being alive doesn't go with the evac scene, or any one after it at all.

No one tells you your father is missing. Someone would have said, all we found was you when we go there. We searched for your father, but couldn't find him. No one under those circumstances is just going to say he didn't make it, he chose your life over his own.

The Archon clearly sees a recreated image of Ryder, still in full gear, helmet and all using the monolith. This can't be a recording of him doing the movements again because he's in full gear, and does the exact same movement, no variation. The Archon then looks at holo image and imitates what it is doing. It doesn't work, so he leaves. If you have the person that did it the first time, and it didn't work for you. You're not going to leave, you're going to bring the prisoner out and say why won't this work for me.

This is ignoring the fact that Alec would have told the Kett from the start I'm not showing you a goddamn thing, you'll just have to kill me.

Well, the game establishes that he wouldn't have to say anything. The Archon learned enough about Ryder's relationship with SAM and the remnant without so much as a word about it. He forcibly extracted the memories to do it. As the creator of SAM, Alec would have been a pretty valuable well of info to siphon.

How is saying something doesn't go with the cutscene having a problem with people proposing other theories.  If I said Tann was working with the Kett, and allowed them to get by the defenses and take the Nexus, people would tell me why they don't think that's possible based off of what was shown in the game.  How is this different.  You're acting like I told you to shut up and not talk about anymore.

I know, but the point is that he would have simply done to Alec what he did to son/daughter Ryder, learn about SAM from his memories, learn that SAM can be used to manipulate remnant technology, and attack the Nexus so he can take control over SAM node. The game would be like 45 minutes long.

Just so I'm following -- the theory is that an unknown force of kett show up and capture the human who's dying without capturing the one who isn't dying, somehow keep the dying human alive without a helmet, revive him, and then interrogate him? (How do they even know which one to take -- the thing this theory is supposed to explain is that they couldn't see what was going on in the facility, so how do they know which one activated it?) Without being spotted by Cora and Liam, who are doing their best to get to the Ryders at that very moment? And Cora and Liam don't even bother to report that Dad's body has vanished instead of being right next to Ryder, where he should have been?

No, in my theory, young Ryder is dead at that point (for 22 seconds) because SAM stops his/her heart for that time period so that the kett leave young Ryder for dead.  Alec at that point is very much alive since he's an N7 trained to hold his breath for long periods of time (remember the story about how it's the N7 candidate who lasts the longest without oxygen who makes the cut).  Also, the Kett apparently don't do autopsies... Remember the salarians... they were alive when they were cut apart.  I also would imagine that the monolith suddenly starting to work would instantly attract any nearby kett patrols back to that site... and they do have 4 minutes to get in and out.

Liam and Cora could think that "Gee, the area has a lot of cliff and long drops; and a person running out of air could become disoriented and fall over one."  Maybe they thought they saw the kett kill him and take the body?  If the AI have a body, why is everyone so vague about how Alec died, including Dr. Carlyle?  When Rdyer asks  "How did my dad die." of a doctor, I don't think he/she was wanting the "like a hero" response... more likely, he/she was expected to get an actual cause of death statement, perhaps even wondering whether or not the removal of SAM from Alec's head could have killed him.

I am revising my theory though.  I think that if the kett did encounter Alec alive, they would have most likely injected him the same way the later did with Young Ryder and extracted memories directly using the device we see.  I still don't buy that the device would have been able to reconstruct that scene in the monolith out of thin air when it lacked the extensive database and understanding that SAM indicates he needed to reconstruct the scenes on Eos.