Splitting slots gradually and non-linear production

I really enjoy the game but I hit a frustrating moment every time I pick it up that makes me step away from it for a while. If I research a specialization such as the engine specialization, I should be able to add a steering assembly slot either before or after the fit engine slot, and the fit engine slot should skip steering. This goes for all specializations.

For example, I research the engine specialization and research power steering. I want to add the fit steering assembly after the fit engine slot without removing it. This lets me add power steering to the car and begin to gradually break out the slots rather than tear up an acre of production line, but the fit engine slot also adds the steering assembly before the car gets to the steering assembly slot. The car effectively stops twice for steering and both stops use a resource. It would be nice if the game would skip a component if a future slot added it. Or even a checkbox for each component in a slot that allows us to turn a component off if we have broken it out down the line.

It would be really nice if I could add components from different “shops” (engine, accessories, electronics) at individual fit slots without following a totally linear order. I don’t see an issue with adding engine valves, then seats, then steering wheels, as long as all of them came after painting. Obviously, you couldn’t add steering wheels before steering columns. This would make sub-assemblies more critical.