Skin friction contributes about 0.04 to the Cd of a compact car. If you were to increase the wetted area by 10%, which is a lot, you'd increase the drag by about 0.004, which is not a lot.
Take a look at the flow across the front of this body:
The airflow's behaviour would be pretty much the same whether the front end were flattened, rounded, or pointed. The center streamline comes to the stagnation point and stops. Any air above that streamline flows above the object, any air below goes below. It turns out round has the lowest drag, but the difference is small.
If you want to move your stagnation point upward, grille blocks and airdams do this. A wedge-shaped air splitter would do it to, and of all the ones we've seen, the one that Mr. Kim brought to the AMEC FE Run looked like the most effective, but it also reduced his approach angle.
Will a splitter that does not interfere with approach angles be too high to be effective? I dunno, but it's probably close. So, a splitter is not on my to-do list.