Grappling? You think they can bring one full-sized ship that close to another and actually physically restrain an enemy ship? If you think ramming is difficult, explain how they can approach that close under combat conditions and NOT collide?
That's even more incredible an idea than the transporter.
I was assuming that they had something akin to "assault shuttles" or if those are added to the game later with greater than 1 square range then "assault pods" would be the default. A small "vehicle" akin to a fighter with just enough fuel and life support to make a short run at the enemy ship. The marines would be wearing full space suits, of course, but could hook into the pod's resources during the trip. If you get there and manage to grapple the enemy ship somehow, then you'd have equipment to try to cut your way inside. Or maybe it would have shaped charges built into it's structure to bLast a clean hole. That's why the component is destroyed on launch. Those little assault pods are disposable.