It is impossible for us to say "yes" to God in and of ourselves (but with Christ it is possible). And I believe that is less a Catholic belief than a Fundamentalist one (I'm not sure what a "hyper-Calvinist" is - the plain variety is scary enough :-) but they would probably remind you that your heart is "incurably wicked" or some such). Our nature is in total opposition to God. This is why we cannot save ourselves through "good works" done apart from Christ - because there is no such thing! No work has any merit (is in any real way "good"), if it is done from a motivation other than love for Him.
Mary wouldn't need to be sinless or without "original sin" if the sinful nature were passed through the human father to the child (as I believe). What do you think of this possibilty? It doesn't violate Scripture, yet does preserve the very Biblical idea that all have sinned and have the sinful nature except one, Jesus, who had no human father.
I don't particularly like the idea (although I think you may find RnMomof7 interested in it). For one thing. They're talking about being able to create life without any genetic material from a male (some kind of cloning offshoot where the child would have two mothers and no father). It appearently works. By your theory we would be creating heavenly children without the stain of original sin. The feminists will have a field day! :-)
Also, I have always thought that the "seed of the woman" refered to Christ because He was the only child born of a woman without a natural father (normally the bearer of the seed) and it would be the only case where ther might be a "seed of the woman". I have read some Hebrew scholars debate this point. If that is so, the rest of us receive the seed of Adam (and his fallen nature), Christ did not. He did not have any generations of the flesh for us to inherit, so we must be re-generated in the Spirit.
I don't mean that no person throughout Scripture ever answered affirmatively to God (of course Scripture is full of faithful servants). But non of them responded in a way that we can now accomplish by simply saying yes to Christ.
But a clone would have the same nature as that which it was cloned from, that is, a sinful nature. Feminists? They all have (obviously) the same sinful nature themselves.