JManM
i think your stance on magic is pretty fair, considering that the majority of the magic in planetos seems the result of sacrifice that more often than not nought tend to backfire even when magic was strong in the world that being said I think warging and taming dragons you don't need to sacrifice anything excluding the hatching of the dragons, but our mc isn't a dragonseed so warging seems a good option to explore (I rly want a jorah riding a bear to battle)
a world that has winters lasting 5 or sometimes 10 years.... i'd looked it up and the ice age killed of 86% of all life on the planet, granted this lasted a million years but that matters little when ALL spieces struggle to get through one winter lasting 3 months. one lasting years might see the remaining 14% adapt but the sheer variable time winter last will see everything death. unless magic fills the belly life in westeros is impossible