By no means do I want to make this small change a big deal, it was just a neat suggestion that I'm sure can be pushed in an update after release. The biggest part would simply be the graphics, which can wait until after release. Otherwise the differences between the two option there, are simply engine smoothness (which affects the luxury rating in the end) versus Engine Reliability and Maintenance interval.
As for where in the UI... If specifically for Variants (Which I personally prefer but that doesn't make it an absolute, obviously) on the valvetrain window (third one into engine design, as it appears on my steam version) We could split the VVT space in half. As there are only ever really 3 options, None, VVT - Intake, and VVT - All Cams. If we divide this section into two that should leave room underneath for a second option selectable as it wont need much space for only two options.
How's that sound?