Queen Christina of Sweden (1626-1689) is a very interesting figure, but her reign was cut short by her abdication in 1654. How would the history of Sweden change if she had ruled the country until her death, and what would need to happen to make it possible?
Even if Antonio Macedo and Pierre Bourdelot were butterflied away, alongside some of the more questionable decisions she took in the later years of her reign, it seems almost inevitable that someone with a personality as peculiar as the one she had - and I'm not just talking about her open disregard of the gender roles of her age, quite a few people suspect that she had something very closely resembling Asperger's - would snap, sooner or later.
What would need to be done to keep her on the throne of Sweden without turning the country into a complete mess?