To me, that would be a sad outcome. Blanche vowed to protect her kingdom that she loves as much as she loves her family. She's working really hard for this. She's even been acknowledged as the future heir by the king himself despite the fact that she is a woman.
Clearly the story aims to be progressive and empowering to women. If she abandonnes everything she's worked for and go rule another kingdom ... that would ruin the plot
As for Verite, I don't know. Can he give up the throne? Would he be willing to? And to whom? Maybe his sister?

Blanche wants to succeed her father on the throne, same goes for Verite. So how is a marriage possible? Who's abandonning their rightful throne to go and be king or queen of another kingdom?