You've piqued my curiosity with "fans of Liara would not appreciate my particular view..." So count me in for any such discussions.
I'll take the initiative and start of the chat convo then since we're all on board. See what kind of crazy shenanigans we can toss together.
I'm probably reading too much into some of the "chosen one" themes which are subtly present, but I remember after my first playthrough before Leviathan came out I left the game with a feeling that Shepard is a special individual "chosen" somehow by the galaxy. Now I'm thinking about it, I reckon this idea was sparked in my brain by Vendetta's talk about "patterns" and Javik's Cosmic Imperative and racial exemplar talks, not to mention the final Stargazer scene about "the Shepard". Of course, a first playthrough is more about emotion than a cerebral examination and later content such as the EC and Leviathan long since cleared those Vendetta concepts up. Nevertheless, they linger in my mind in some nebulous form.
Well even the Leviathan seems to speculate there is something 'special' about Shepard.
"You are an anormaly"
"Your victories are more than a product of chance."
I kinda like to think that last line is foreshadowing that Shepard was destined to finish the reapers. That it was fate deeming he be 'the one'. The reapers spent eons experimenting with the galaxy and now the galaxy is fighting back. Of course, refusal kills that little fantasy. Still its fun into stuff from time to time.
You and Vazgen aren't helping me any as much as I'm enjoying it
So now I can't fall back on the Shepard is indoctrinated because the IT is false, I can't fall back on Shepard being implanted by Reaper Tech which is why he got hit by the Destroy beam, so what am I left with? A Catalyst who appears in a form only present in Shepard's mind with no explanation as to how it is able to do this; and a Destroy beam which targets "technology you rely on" as well as Synthetic life including Shepard.
Well any of that could work if you take a few liberties with your headcanon. If people get more satisfaction and enjoyment from headcanoning IT, so be it. I played a few "IT" headcanon playthroughs and thought it was pretty entertaining. Whatever floats your boat. Long as you remember where the fanfiction begins and the canon ends, if that makes sense.
Though, again, and I know Vaz sees it differently but you could just assume the starbrat is not literally, in-lore meant to be the same kid. If you assume its just a reused but modified art asset then you don't have the problem of "how is it the kid from Shepards dream?"
It's only a problem if you allow it to be a problem.
Vaz thinks it is the kid and the reason Shepard says nothing is because he's smart. That is a valid thought, nothing wrong with it. If thats how you want to see it then thats fine, it isn't really contradicted. I just don't think it is the kid because Shepard doesn't mention it. I don't give Shepard the 'smart' pass because of how stupid Shepard has been throughout the entire ending.
Also the Leviathan DLC where Shepard, logically, should realize he isn't really speaking to Ann because he's in a mech deep under the water of some alien planet. Yet he stills takes instant notice to the Leviathan taking form of Ann and refers to it. He doesn't just silently formulate that "oh, I see, you're using an image taken from my mind, you're not literally Ann."
In the mission where Shepard enters the Geth Consensus he should really be able to understand that the world is being made into something he could understand and yet he's stumped by it and mentions his confusion. He actually had to get it clarified. I'm lenient on this though since, in all fairness, the geth consensus isn't really 'normal'.
At any rate it seems odd to me that Shepard is confused and ignorant about these very similar events and makes a point to remark on it yet he doesn't say ANYTHING about the kid. The kid is a far bigger deal than Ann Bryson. This isn't just some scientist he met earlier that week. The starbrat is the form of the child that has been haunting Shepard's dreams since the beginning of the war and has been making it difficult to sleep. The child should be far more significant to Shepard than Ann yet he never remarks or bat an eyelash to the catalyst's form. That tells me that it isn't MEANT to be the exact same kid.
They not only took efforts to distort his image they even distort his voice by overlaying it with male and female Shepard's voice actors.
Ha, my Shepard hit that and survived 
I dunno, I can't ignore the fact that the Catalyst is seemingly able to read Shepard's mind. Take that little fact away and I'm with you 100%
Ah but did you actually see them embrace eternity? There's no reason you couldn't sleep with an AY. They only kill you when they embrace eternity. We saw handprints against glass.
You don't have to assume the cataylst can read Shepard's mind, though. The only thing that points to that is if the form the catalyst takes is LITERALLY the same kid from Shepard's dreams. Assume otherwise and you no longer have any reason to assume Shepard's mind is being read by anything.
If you remove that, then how do you explain shooting the tube? Or you think that the Catalyst is capable of transferring images into Shepard's mind but can't extract images from there? Don't forget that there was this whole standoff with TIM when they could probe Shepard's mind for information.
Again we should keep in mind the subtle differences between reaper indoctrination. Placing images in someones head is not the same as taking images out. Just because you can send signals and information into someones mind doesn't necessarily mean you have free range to take information. Subtle signal-based indoctrination turns us into receivers where as the extreme nanite variation turns us into both receivers and transmitters.
For perhaps a little context on the difference between transmitting and receiving look at the Asari. Liara is able to rather calmly and pleasantly share one of her memories with Shepard. Yet when shes taking memories out of Shepard's head it takes a toll on her.
Also look at the Leviathans. When they are directly controlling Ann, making her both a receiver and a transmitter, the toll it puts on her can practically fry her mind if she stays connected too long. Yet the ones at the research facility who are just mindlessly following the orders given to them but not directly controlled have been able to endure being receivers of the signal for years. This a flaw with both reaper indoctrination and leviathanation. The more control you exert on them the less useful they become. You fry them out. Tell them what to do and leave them to do it and they can last for decades.
Finally look at the collectors themselves. Typically a collector drone just follows the orders given to it. Yet when direct control is taken, which by its very nature would require turning it into both a receiver and transmitter, the effect it has on their body is extreme.
For the reapers to be able to draw an image from Shepard's mind, based on what we know about their process of indoctrination, would require him to have reaper nanites. These are the most extreme variation of indoctrination and if he was under this level of control then they would not need to do anything - Shepard would be theirs. No hope for that. Which clearly cannot be the case because the control ending.
"He couldn't control us, because we already controlled him." Shepard isn't being controlled by the reapers yet for them to get the image from his head they'd have to be indoctrinating him with nanites to read his mind. In which case Shepard couldn't control them.
Indoctrination is a subtle process. One does not become indoctrinated in a few minutes. It is also connected to the Reaper technology that is responsible for indoctrination. Notice how Arca Monolith destruction stopped (IMO only paused) Jack Harper's indoctrination.
Did it though? The protheans VI mentions there is a pattern that persists in every cycle. In their own cycle they had their own version of Cerberus where they argued the reapers should be controlled, not destroyed. They were indoctrinated. The Illusive Man was working according to their plans all along, he was this cycles agent for causing inner-conflict with the organics and fighting for control of the reapers, just like in cycles since passed.
Deep stuff, man.
The problem I have with this is the Catalyst's motives in using Shepard. He says he can't activate the Crucible (or something like that) but that doesn't seem to be the case. If it Control the Reapers can't it order a husk to shoot a tube or chuck an organic into a beam of light. If it wants a specific option chosen it should just do it itself.
Or it actually things Shepard is the best person to make the decision, in which case why would he try to emotionally affect Shepard? For what purpose?
Good points. More reason to assume it isn't meant to be taken literally as the same kid but rather just a reused modified art asset.