Interesting ideas there.
I'm not so sure about the grill ramp, it would still be a pretty steep angle and it would still slow the air when off road. I already have mild temperature issues as it is (even at highway speed). Ambient +120f and ambient this weekend got up to 108f.
I'm going to vent the hood and see if it helps.
The air dam, were you visualizing that as vertical or slightly sloped? If its sloped I could make it solid and able to slide up on rocks.
Closing up the gap between the fender and the bumper would still be pretty steep, but should be better than a gap, and should strengthen the fender considering I'm going to remove some material above the tire to fix some mild rubbing.
Btw, that the same color as mine, but its not near as shiny, and I don't have a 4" body lift.