If you do indeed stick to what the Bible says, you must realize not-Mary's-ovum is possible.
One difference is that, in view of the whole bible, "P"erpetual "V"irginity is exceedingly more difficult to defend. Funny how the RC system embraces the easy assumption -- without any biblical evidence -- that her egg was involved in His conception, and refuses to do the same regarding His brothers and sisters. Of course, rethinking either of those would diminish her role in their system.
Yet, the real difference is that the RC system cares not about possibilities. Until such time as it receives Another Official Special Revelation, it has done all Christendom the great service of removing any such mysteries from the Word of God.
It may be. But, thank the Lord, I am not left to my own devices.
You have still not even attempted to address how Jesus redeems humanity if he is not one of us, if he does not assume the fallen humanity in order to lift it up.
SD
If, over the Easter weekend, you see video of two men picketing in St. Peter's Square, with signs reading NOT MARY'S OVUM, you'll know who it is. ;o)