I'm really itching to do something exploring "West of Westeros" - the weird Lovecraftian places that are never going to get fully explored and fleshed out in the series beyond World of Ice and Fire. Adventure, mystery, intrigue, and lots of fun esoteric stuff.
I'd love Jaqen, Sandor, Syrio, or possibly a really interesting OC to accompany Arya on her journey. Definitely looking for romance to be part of the line but I'd like to focus on exploration and worldbuilding and mythology.