So I was reading a couple of sugestions. First, here is a lot of suggestion on the engine builder. The reason is that since it is the final deal it’s easier to see what is missing.
You answer most of the suggestions stating that you don’t want to overcomplicate the designer, and you are right, it is already complicated.
So my suggestion is:
Give the ability to buy engines built by other players.
When you are making a car instead of using your crappy engines, you are given an option on the “choose the engine” to choose from other players offers.
Also make the choose option on the car builder appear before you get to the engine tab.
When you buy engine you only see the stats that we currently see on the last section of engine building and all other options are LOCKED.
This way people less skilled with the mechanical stuff can enjoy the game without being annoyed by the engine warnings they don’t know how to fix.
And players that prefer to build engine get to make money out of it for building more engines.