I think you're taking that comment way too literally. They have a final script for a good while, they're heavily in pre-production now. They won't rewrite the whole movie based on reactions to TFA, especially not after its success.

Rey was left by her parents (or people who acted as such and that she believed to be her parents, like adoptive parents), it's in her POV in the books, it's in the Force vision in the novelization as well (less clear in the movie as they showed the ship depart without including the good byes like in the book). It's been confirmed by canonical sources that she was five when she was abandoned (I didn't know that yesterday). Like any 5 y.o. she must know who she is. She yells and cries when her parents leave, she's not been "memory wiped"like some believe (silly idea). She just had no reason yet to tell the other characters about who she is, and she may even have personal reasons not to (it's even speculated that Rey is a name she's made up for herself on Jakku).

Kylo Ren doesn't have a canonical age so far, but Pablo Hidalgo says he's late 20s (the actor is 32). In TFA Rey's 19. At n most their age gap is 10 years, probably less. It doesn't make any sense whatsoever that Leia would had hidden her pregnancy back then when Ben was only 10 or even younger, nor Luke's wife (the idea that they'll have Luke Skywalker father a child out of wedlock without even knowing about it is completely silly (this is SW - as non confrontational a series as can be, not Game of Thrones). Jeez.. not only they specified that Han and Leia are married and not even divorced (just estranged), but they also made sure to marry Padmé and Anakin on-screen before they had sex.

"Early on" is speculation based on a single line in the novelization that's pretty open to interpretation. Leia says he had been influencing Ben "almost from the beginning", at first from the shadows. She wasn't aware of that, she discovered this much later, probably even after Ben has turned and joined Snoke or espoused his ideas openly, or started openly to challenge Leia and Luke about Vader and the Empire vs. democracy and the republic.

People willing to jump through hoops to make Rey Leia's girl or Luke's have jumped to the conclusion it means "since Ben was a young child". But that statement as other much more likely interpretations, such as Snoke influencing Ben almost from the time Leia started noticing signs of darkness in him, or almost right away after Snoke or the First Order appeared. We can't be sure what Leia meant by "almost from the beginning", but it's far more likely to refer to an event, not the childhood of Ben in a general way.

Leia hid what she could sense in Ben from Han, because she thought it could worsen the situation if Han tried to interfere (she also admits to Han she might have made the wrong decision), which pretty much means that Ben was old enough to have developed a conflictual relationship with Han, and old enough that an intervention by Han might antagonize Ben further. It also means that Ben was old enough to be reasoned out Leia rather chose to send Ben to Luke, which turned badly (and probably quite fast, as Leia tells Han when she sent Ben away is when she lost him, and lost Han). He was probably a teenager when he started showing signs of darkness and wrong political ideas... Rey was already a little girl, too late to hide the fact she existed.

Of course he would, but it makes no sense that Snoke wouldn't know about Leia or Luke having a daughter if he knew Leia had a son.

And his solution was to dump his little girl alone on Jakku and lie to her that he'd return soon? You really have a great opinion of Luke, or Han and Leia.

And one of those mistakes was tying things up way too neatly and creating too many convenient connections.

But anyway it's too late. Rian Johnson wrote his script around the ideas of Abrams/Kasdan for the next two movies and building from a rough cut of TFA. There's canonical material already confirming that Rey was left on Jakku by her parents.

Disney wouldn't have spent millions on pre-production for the next movie if they intended to run every plot point of TFA by "the fans" (and I'll point out to you that many fans would prefer Rey not to be Luke's daughter or Leia's, as this is too obvious), they would have postponed the movie to 2018 and wait to see the reactions to TFA.

Don't forget one trademark of Abrams's stories: he likes to mislead and surprise his audience, and he loves to plant false clues and red herrings and to distract from the real mysteries. TFA is full of questions and mysteries, and going by Abrams's history, the answers are most likely not at all what "everybody" think they are.