At this point it would essentially be a bait & switch.
She's exhibited traits of MANY key players in the Star Wars saga. She's strong, self-assured, and defiant like Leia. She shares Luke's wanderlust, natural piloting skills, and force sensitivity. Her scenes on the Falcon showcase her mechanical inclinations, and ability to adapt creative solutions to render escape, very Han. Scenes of her scuttling stealthily about, and scaling walls with silent grace in the Starkiller base are very reminiscent of Obi Wan Kenobi (and let's not forget that English accent) ...a friend of mine even expressed that some of her scenes on Jakku, like scavenging parts and wearing the X-wing pilot helmet with child-like wonder, reminded her a bit of a young Anakin on Tatooine... all very purposefully an amalgam of our saga heroes, and I believe with the intent of keeping the viewer guessing about her mysterious origins.
Stacking all these clues to her possible lineage could set up the ultimate twist that she has none. That she is her own person, illustrating the fact that the galaxy is full of heroes without being born to a particular bloodline, exploring different aspects of The Force through Rey for a new era in the Star Wars universe... A concept easier to relate to, and be inspired by, especially as her story unfolds in the trilogy.
Building a mystery only to subvert it is the ultimate waste of dramatic potential, not to mention story that could have been included in its absence. It might be charming and refreshing in an epic 5-book fantasy, but when we're talking a movie with a 2 hour runtime that is a very inefficient use of those precious minutes of screen time.
But what mystery are they building? And if Luke is Rey's father, then what is the mystery? Other than some various parallels, we actually have less to go on than we did with Luke's parentage in a New Hope. Besides, to "subvert" it would be what's called a "red herring", a misdirection, and only serves to expand the potential for a compelling new story. Especially since these clues are not as strong as other direct character connections were in past movies...
In the first films, much emphasis was built around Luke's father:
Aunt Beru and Uncle Owen's discussion of Luke having a lot of his father in him, which is what Owen was "afraid of". Ben tells Luke a whole story about his father, which gave great weight to Vader's final reveal that HE was Luke's father. Aided by Luke's "Force vision" on Dagobah.
In Empire we get a line eluding to a second hero: "No, there is another". And from what I've read, that line was not meant to be about Leia, but a new female character to be revealed in the third film. But was changed to be about Leia in an economic rewrite to move the story forward, but helped to serve as another twist that Leia was Luke's sister.
We even get more clues about Anakin's mysterious lineage in Phantom Menace and Revenge of the Sith than we do about Luke and Reys connection in The Force Awakens: Shmi's reveal that Anakin was a "virgin birth" and Palpatine's story of the force manipulation to create life by the dark side, is still more to go on than anything we've seen about Rey's past.
But my point is that we get more parallels to other characters other than Luke in Rey's characterization, and very few direct leads. So much so that a lot of speculation leads to other characters; like that perhaps she's a second "love child" of Leia and Han that Leia kept secret from Han after they become separated, or that she's Obi Wan's grand-daughter, what if she's Grand Moff Tarkin's grand-daughter? (how ironic would that be?) ~ but there's enough intrigue in her character to allow these other theories.
Even in Rey's "force vision", while yes we see Luke, but also the Knights of Ren, and the voice of Kenobi calling to her, not Luke. None of these images make a direct connection to Luke, but only serve to depict direct events both past and future, prior events that a very young Rey may have been apart of not because she's Luke's daughter but possibly was a padawan youngling saved from the massacre, resulting in her exile on Jakku by her "parents", who ever they may have been, if they were even her parents to begin with. She has as much connection to R2-D2 as Luke in these scenes. It's so much more vague with very few direct connections than in previous Star Wars films about other legacy characters.
I feel this new film's use of familiar territory is to ease us back into the Star Wars universe we're most comfortable with by design. With it's many parallels to a New Hope and Empire being used as a launching pad to set up new stories and characters for a subsequent trilogy. I feel that it purposely teases a well used, family specific, plot device that could serve to reveal a much different twist and a compelling new story exploring more of the Star Wars universe.