Well said.
The process for a custom build like this is a bit different than our "normal" process. In this case we'll build the body/chassis like normal, but when it comes out of the mold we'll move it over to assembly instead of into my body shop. This way we can dive into drivetrain and suspension fitment. This allows us the most flexibility to make changes and fabricate without having to move backwards anywhere. In addition, for this particular build, there are some unknowns that will effect other choices in the build, such as suspension/brakes will dictate wheel options to an extent. Once all of that is done we'll disassemble, send components off to their respective rebuilders, and the body/chassis back to the body shop boys.
As for the "normal" process, some guys like to lay it all out in the beginning, others like to make the minimum required decisions up front and then once it is closer make the final decisions. I do this via phone, e-mail, zoom or in person.