What if Jenna-Louise is going to play Amy's next regeneration?

So, what if Amy is actually the Doctor's and Romana's daughter? Maybe the Doctor got Romana pregnant, and she ran off to Earth before the Time Lock engaged. Romana then used the chameleon arch in her TARDIS to turn herself into a human. The chameleon arch had no effect on the unborn baby, allowing Amy to have regenerative capabilities. This could explain Amy's memory abilities and River Song's Time Lady traits. Also, the reason no one ever noticed this is because Amy has always had perfect health, so she was never taken in to a doctor's office.