I myself think that there is a strong argument for an entirely separate Space Force. The arguments I find most convincing come from our own Air Force Doctrine, and history. First, we believe, that Air is a separate medium, requiring a specific kind of strategic and tactical thinking, and that airpower is best understood by airmen.
Space also is a separate and very different medium.
If air power is defined by it's speed, ubiquity, and three dimensionality, space is presently defined by geometric placement, periodicity, infinite loiter, wide coverage, and high vista. Second, we believe, that for Air Power to have reached it's pinnacle, it needed to be free to think in its own terms, and not be eternally the handmaiden of ground power, where it was simply a sophisticated artillery. Third, victory has shined upon those who anticipate changes in the character of war, on not on those who waited to adapt themselves after those changes have occurred. We don't want to be caught like the allies did, when the Germans saw the application of Armor in an offensive light, and took their doctrine from the Allies who failed to organize themselves for victory. Fourth, there are very credible, asymmetric threats to our national shores, and the survival of our way of life.