That looks great! I had the very same thing planned, but I scrapped the scout figures because they seemed too small compared to Universe Dirge. Instead, I'm using Armada Sideways, Energon Slugslinger, Movie Breakaway, and Movie Grindcore as the limbs.
I'm really going to have to look into getting a bionicle or lego knight since the joints look much better than the ones I'm planning on using. Keep up the great work, I can't wait to see the finished product.