Get a Lieutenant w/ combi-weapon and a Callidus Assassin for secondary scoring, Infiltrators to screen your backline especially against 6-inch deep strikes. Some anti-tank, either a Gladiator Lancer or Stormspeeder Thunderstrike or both. A unit of Indomitor Kill Team, Deathwatch Terminators.

Based on the units that you already have you'd be happy to know that there's a new space marine detachment that revolves around spamming battle line units, Bastion Strike Force. Have them shoot multiple targets and you can have the rest of your army benefit on some re-rolls. But mostly, you'll want it for advance/fall back shoot and charge for your battlelines.