Hmm, I think the main objection I would raise is that River seems to be living in mostly, if not entirely, opposite order to the Doctor. I feel like she is bordering on too old to have the baby later and not know about it yet.
Yeah, this is where my thoughts are going too. Either she's not had the baby yet, in which case when does it happen, because we know the rest of her life pretty well. Sometime post-Time of Angels and before the Library? (That fateful picnic at Asgard?) It would be... tricky to fit in.

The alternative - that it happened earlier in her timeline, doesn't make sense what with being clueless about The Girl and what it could mean. Unless she's been mindwiped, but how and why? (Did the Silence steal the child and mindwipe them both? Because they would tear the universe to pieces...)

So, basically I love the idea to pieces but can't make it work because the timing seems all wrong. And then we add the parallel universe thing and my head starts hurting again and I think I'm going to hide... /o\