While discussing the possibilities and impossibilities of exchanging Royal offspring and heirs in times of turmoil is amusing, it doesn't bring you much further in search for the truth. What you accept as possible is your point of view and so called proofs usually are pretty flimsy. Looking at the usual suspects, though, might give you some new ideas as to whether it should or could have been done or not.
Christina of Sweden was five when her father King Gustav II Adolf fell in the battle of Lützen. Upon his death, her mother Queen Maria Eleonora was put under house arrest and exiled to castle Gripshom. On the express wish of the king, Christina was raised and trained as a prince and not a princess. At 16, she declined to co-rule with a regency council; instead she took full control at 18 when coming of age.
Queen Berta of Burgundy, formerly Princess of Swabia, Queen of Upper Burgundy, and Empress of Rome, was buried in Payerne, a small town in today's Republic and Canton of Jura, Switzerland. She was first revered as a saint there, but her story started to grow as time went by. Soon she was known as Good Queen Berta. Still later, she acquired the name Queen Berta the Spinner. Even later, she would become godmother to a newly established republican state. And her story lives on today.