There is a great deal of space in which you can play with this topic.  It seems wide open.  I would focus on how the letters and poetry of Keats really stresses the idea of Romanticism and Keats' own place in the pantheon of literature.  Part of what makes Keats' work so powerful is that he was so young and was only a part of the literature scene for so little time.  Yet, he fully grasped his function on this stage and understood his place amongst the greats.  His letters reflect this grasp of English Literature and his place within it, while his works reflect the same reality.  I think that this deep and profound understanding of the history of Romantic literature is something that defines him as a Romantic thinker.  It is this aspect that can receive significant attention in any paper.  While all of the Romantic thinkers and writers understood their place in their own movement, Keats was one of the few that helped to integrate the Romantic movement into the consciousness of Western Literature.  Much can be written on how Keats brought this out in his writing and in his personal correspondence.  This makes Keats a product of his time and a reality that transcends it.