William could be the one who takes the fall for Malrik. Let's him advance in the lists but he owes a favor. Or they could have a straight contest. Just some ideas. 

[@Masterkeun] Have at it! 

[@Asura] A lot of the major Houses are still unspoken for. Martell, Greyjoy, Stark, and Tully aren't being played by anyone. Also the Velaryons are a pretty important House now and there are many other notable families. Or House Thenn as I think you expressed interest for. You could always be a travelling adventurer as well. A Bard, an alchemist, a merchant family with aspirations, a holy man, any variety of Essosi type characters. There's a lot of different things you could be in this world.