OK, let's talk about mechanics
There are few I still try to decide on, so I could use your input here.
I could use some ideas on
distribution and
marketing mechanics.
First, how it works:
There are 6 continents/regions (markets), you put models on those markets. You start in one region, this is your home region and you get several advantages selling there (no tariffs, cheaper distribution, boost to marketing, etc). So, there is a significant incentive to first focus on your region before expanding worldwide.
There is one controversial design decision, you have only one factory. The reason is mostly so boring distribution (sending cars around) is removed and instead so you could focus on the grander scale of things (strategy instead on adjusting dozens of offcies and factories). Another reason is that I want to make production somewhat more complex (so you have more upgrade options like upgrading specific machines and manufacturing processes; which works best if you have just one factory so the player is not overwhelmed).
Design goal:
Mechanics should promote a gameplay which does not force you to produce everything (so it does not turn into micromanagement hell at later stages). So, there should be mechanics that promote focusing on several types of models only (while allowing to produce everything if player desires so, but this should not be the optimal strategy).
About
distribution costs (
looking for ideas and comments here!):
You open offices in regions. Those boost your selling power in that region. Those have upkeep.
Next, each car you put on the market (in a region) has a fixed distribution cost (so putting 100 types of cars while selling like 1 car per turn each means bankrupcy). I am considering a steep distribution cost (if you have 3 cars being sold you pay $2,000 per car in distribution costs; if 4-6 cars $3,000 per car and 7+ $5,000 per car) to further encourage not putting tons of cars on each market.
About
marketing (looking for ideas and comments here!):
I was thinking about a "car type" image, so if you market a sedan model X it also boost your sedan image and if you introduce a new sedan you already get an image boost (so, focusing on a limited number of cars would be benefitial).
Also maybe a mechanic where you select 1-3 cars (per region) to be "on display" or "have a marekting focus" and those models would get a boost to sales?
Overall, I have not thought much how marketing should work, so I'm open to suggestions.
About
production complexity pts:
There is also another mechanic (already implemented) to encourage focus. Factory (remember that you have only one factory) has Efficiency bonus. It's based on "production complexity". Complexity increases the more widely different cars you introduce. For example making 2 sedans is less complex than making 1 sedan and 1 coupe, also if the produced cars use the same engine and chasis it means smoother production.