A few of my ideas!

Twin chargers - A turbocharger and a supercharger linked in a setup which eliminates turbo lag
VTEC - Variable valve timing and lift electronic control maybe with a slider that you can change which RPM it engages at
Electrohydraulic valves - Uses no camshaft can achieve higher RPMs and lower RPMs also superior throttle response and acceleration due to less friction. Improved economy and emissions

Hey durr, it is cool that you are thinking of things to add to the engine designer.

However, as far as I understand you, asking for Variable Valve Timing, that’s already in the game…
And all the other details you mention are surely nice, but time taking and not the main focus of the developers right now. The engine designer is finished for now, until the tycoon part is implemented and the main work on the game is done…
If you feel like looking around, there are many topics concerning new ideas, some of which you have mentioned even, including responses from the developers!

Next time before you suggest, please use the search function. Or read the FAQ. The engine designer is currently on lockdown, which means, they wont add stuff to it until the game has the tycoon part done. Also, Adding more options to the engine designer like VTEC and Electrohydraulic wont be added, because it will add more complexity but very little gameplay. As for Twin chargers, they will come, eventually.