I like the idea of keeping it simple! You could consider adding a touch of Carafa or chocolate malt for color (optional), and well what are your thoughts on "Aromatic" malt? I haven't used it in years, but it shows up in my old recipe for a doppelbock, maybe I should taste a few kernels again sometime as my memory is fuzzy. But of course, you don't need to add anything else to your recipe, it will turn out great of course.