I suddenly need this. Oh this could go two different ways in my head.
1) Either Prince Crono escapes from the palace and meets Marle. All the normal chaos ensues with some obvious changes. 2) Princess Marle gets dressed up for adventure and goes to the millennial fair. She meets Crono the same way, gets sent back in time, BUT she rescues herself before disappearing. Crono and Lucca come back to find her slowly fading in and out, while she fights back to stay. The three of them then sneak out of the castle to rescue the REAL queen, meeting Frog on the way. And so on.
I don't know which one I like more but I got two different plots now in my head that won't leave because of this.