Re: Something Star Hero needs, but hasn't.
Hmmm. First off, How do you fold space? Using EM as an analog [and recognizing the difference between EM and gravitation, specifically while EM is a vector force, gravitation is a tensor.] You could use something like constructive interference to create banded regions of, well, "compressed" and "expanded" space-time around the ship. Using Alcubierre's technique as well as later modifications, one could produce a warp drive that way.
Wabbida again?
The point is you need a working model of the physics first. From that, you can design the equipment and arrange it as needed. You can look at power requirements (Does the theory allow for something analogous to catalytic or resonance reactions? You don't need that much energy to produce the effect, you just needed it directed to the correct zone, or using the correct material) and energy densities as well as efficiencies. This is really what determines the space, size and weight of your starship engine.
Most of the tech for a starship is already available. Life support, hull materials, navigation, computers, a lot of this stuff is already here. What we don't have is the engine, the actual propulsive device. Once you have that, you know how much power/fuel it takes.
As "tech level" increases, equipment efficiency increases. Size, and weight decrease as does power and/or fuel requirements to produce the same effective speed. (This is true of almost all the components, not just the propulsion system.) Prices for new, state of the tech level, stuff may be more expensive, but lower tech items become less so. Or as Bucky Fuller once said, the entire direction of technology is to do more and more with less and less.
There may be also some key technologies or theoretical models that are applicable across a number of starship systems. For example, imagine being able to manipulate gravitation in an analogous way to EM. Not only will (might) gravitational technology allow you to create a warp drive. But also such things as pumps that are more efficient with greater capacities, higher flow rates. etc. Or note how in Star Trek, having transporters automatically gives you replicators.
So, for building a design system, you have to start off with a theoretical basis for the drive system. Once you know that theory, a lot of the other pieces are already built in the real world, or extrapolational (?) from real world technologies. The size, mass and weight, as well as power/fuel requirements fall out.
I spend waaaaaay too much time thinking about such stuff.