Ok, for your scouts, I recommend dropping one of the bolter squads. With that, I suggest giving one or more of your Assault Squads a power weapon or fist just to add some versatility. Use the other left over points to give your other scouts with bolters a land speeder storm to give them mobility and to help contest objectives. Perhaps also give that SGT melta bombs or a power weapon, combi bolter or something.
I like the idea of trying to work in Vulcan to make your signature weapons more reliable.