[PvK]

Well, maybe if you did something with the life suport, bridge and/or crew quarters components, because those affect movement if they are missing. You could decide one or more of them was unnecessary, and then use that ability as a required widget for the engines, probably.

Or you could use bonus movement for your engines, and standard movement for your widget-that-makes-engines-work, because the ship needs to be able to travel at at least speed 1 via standard movement, before it will move at all via bonus movement.

PvK