The important missing piece here: The rocket engine subsumes both drivetrain and power plant.
In order to build a proper jet engine you need to have both a jet drivetrain and a turbine to power it. So for the rocket engine, you need to have a rocket drivetrain plus a rocket power plant.
Yours is 200TH, 1 EP, 10 vl, (which is a little better than mine at 70TH, 5 vl, 9vl fuel/hr, Cr700 per unit).
We now need a rocket power plant: 120 vl per hour, 1 EP produced, 2 vl. This make the rocket 8 vl in size. This now lets you overproduce rocket power plant, for the additional agility.
Final Stats:
Rocket drivetrain: 200TH, 1 EP, 8 vl, Cr700 per drive unit.
Rocket Power Plant: 2 vl, 1EP, Cr 700, 120 vl per hour. Note this is a terrible fuel consumption but it produces thrust on the order of the Grav units. The Rocket drivetrain requires a rocket power plant, and the only drivetrain the rocket powerplant can produce power for is the rocket drivetrain.