It looks like the system only uses rocket engines. I don't see any provision for jet engines in the drawing. If you could maintain a very steady thrust with the rocket engines, you might be able to adjust the airspeed enough to fly formation by using drag brakes like the ones on the F-16. The F-15 drag brakes seem too large for precision control. The drawing shows multiple rocket engines so perhaps they plan on controlling the thrust using a combination of throttling and perhaps shutting down an engine. Many of the X planes used the same engine as the X-1 which consisted of 4 rocket chambers. I've read several flight reports where they controlled the thrust by turning the chambers on or off individually.

The drawing isn't very clear but it appears the cargo bay is right behind the cockpit. From the looks of it, the bay volume is very limited. Carrying the payload externally might be possible but it presents some problems. First, there's the added drag. Second, there are center of gravity issues. Lifting-body aircraft like the one shown in the drawing have narrow CG windows. Third, there's the problem of location. If you mount it below the fuselage, you run into ground clearance problems which might require longer (heavier) landing gear. If you mount it above the fuselage, you have to make sure it doesn't interfere with the refueling ports.

There's another question that comes to mind about the refueling - will they use multiple booms (one for the oxidizer and one for the fuel) or is there a safe way to deliver the propellants in a single boom, perhaps with two pipes mounted side-by-side or even coaxially? Mixing the propellants in the tanks can get very unhealthy, especially with high concentration peroxide.