What is good design?
I think a good design can be split into three elements:
#1 Purpose. What is the vehicle’s function? What is the context - the world or physical conditions it operates in? What is the history of it? I would include here also the purpose of the artwork. Is it for a feature film, cute cartoon, mobile game with limited screen space? The choices need to fit the context and criteria but can also draw inspiration from it.
#2 Big things. When we take the purpose and start turning it into a design we should 1st consider the big aesthetic things. Silhouettes, big shapes, stance, balance, distribution of visual mass. If these things are messed next step will be somewhat wasted.
#3 Small things. The last thing to make design really sing is the details. Often it's this part that really gives the design footing in real world - or whatever the context might be.
Naturally these three things overlap and influence each others. The design process is a loop where you go through all aspects at least a few times before you tighten in for the final.