I think I'd be interested with a couple ideas, wondering if they'd be possible before thinking of settling on one.

-Carling Merchant Prince coming to the crown lands along with significant rumors of armies of mercenaries and petty nobles massing in Foronia. I'm thinking him being actually absolutely not interested in rulership and just wanting to make sure the new king or queen, whomever it may, won't screw over his business with things such as ridiculous taxes.

-Chlotaric Prince coming out of nowhere with riches and unnatural charisma. The secret behind him being that he's a demon worshiper that was granted otherworldly favours to claim the throne and destroy the Faith.

-Honest to god Knight and head to one of the most military powerful house of the nation who firmly opposes the idea of a queen because he thinks a woman couldn't have the right values to be proper leaders. Despite the misogyny however is actually a great selfless guy with a flawless sense of justice that want what's best for the realm & someone likely to lay down his life for the queen at any moment should she prove herself to him.

Maybe more ideas later... thoughts?