Although the vagina can stretch to accomodate the passage of an actual newborn child, I do not know of any women who found the experience pleasurable.
I think, if you research the information correctly, you will discover that the vagina is an expandable organ. Unarroused, a female's vagina is only 3 to 5 inches deep. When arroused, the vagina "tents" and lubricates to accomodate a penis comfortably. The vagina can expand to accept larger than average penises, but it is not comfortable and pleasurable in ALL cases, as some women are smaller than others.
So, to sum up, the vagina can expand from pinky size to baby size... cool, huh?
As far as your other ideas, I would discard them if I were you. Ceasarean sections are more dangerous than vaginal birth, and leave the woman scarred. There is also a higher incidence of complications with C-sections later in life. My wife had 2 C-sections because she had problems carrying to full term. She ended up needing a complete hysterectomy because of all the scarring and problems with her ovaries and bleeding.
I selected my wife as a partner because 1) our personalities mesh very well and we respect one another 2) I enjoy talking to her 3) I think she's beautiful and sexy and fun and 4) we are sexually compatible and enjoy making love with one another. That's the four basic ingedients of a good relationship.
I don't know of any way to tell if someone has a big pussy or small pussy without actually having sex with them.