Interested in peoples views:
positech.co.uk/cliffsblog/2017/0 … n-dilemma/
While reading the post, as you were explaining resource units I started thinking “maybe varying the assembly time would work…” 
I do like the idea that sending different chassis types down the same production line might create some optimisation challenges to solve vs having a dedicate line per chassis. To borrow your example, SUVs might clog up the ‘fit doors’ slot requiring a second one to be built, but a line without SUVs could get by with one slot.
From the UI perspective, could the info be show in the Time indication for the slot? When idle it could show something like:
Time: 2m 45s (Compact -15s, SUV +20s)
When the slot is running it would show the time for the active vehicle type:
Time: 3m 05s (SUV)
Nice idea on the brackets there. I did indeed think that it may be interesting to do this because it opens up all kinds of cool optimisations where maybe you have to do 3 compacts then an SUV then 3 compacts…in order to maximise the efficient use of your robots 
varying the assembly time is a nice improvement to the game
what I am proposing is to have a market area where it shows you a forecast for market requirements ( for the next xx days ), and also the number of vehicles that you have in stock, and you should be able to see ( via some graph ) how the car output will fit to the market needs