The only way you're going to make a useful pro machine is to have one with standard parts that can be upgraded easily, something Apple absolutely refuses to do and has refused to do in any of its products for many years. That's why the last decent pro machine is 7 years old and why I'm not holding my breath for the next one. It's guaranteed to be proprietary like all the rest of their hardware these days. Making a pro machine is not that hard. It's by far the simplest type of machine because by definition it should be able to handle anything. Hobbyists and corporations alike have been building them for decades. The fact that Apple can't build the simplest type of machine says a lot about them as a company in 2017. None of it good.

EDIT: Discussions around minimalism and design at this point are beyond irrelevant when Apple can't actually build a computer that serves pro users' needs. Those factors only come to play when you actually have the ability to build a proper product. Apple does not have that right now.