Choice of cam material and manufacturing process.
Possibility of hydro formed hollow cam.
Since I mentioned hydro formed, perhaps we can get this added to the car designer. I’ve seen this used on newer Corvettes. They use an aluminum frame that is hydro formed. The process allows the frame to be hollow (lighter) and precisely and reliably be bent into shape.
I like the suggestion of cam material but the engine designer has been finalized. However it’s probably something that could be added as a mod (again). The manufacturing process will probably be some choice in the tycoon part of the game where cost and quality will be proportional? (Maybe the devs can clarify this).
As regards hydro formed I couldnt say either way but it sounds like its a relatively new tech? Game spans from 1946 (i think) to 2020 so dont know if it will be included if its such new technology.
Keep the suggestions coming though, they are great to ponder about! 
The aluminium chassis you are talking about will be in as aluminium spaceframe option, so yes, they are planned.
Regarding cam material, Drummerdude is spot on 
it is too in-depth for a tycoon game that needs to come out before year 2020