Interesting, and tempting. But to get NAV, either you're depending on your cell phone (Android or Apple), which can be annoying, or you'd need the AVIC-U280 add-on ($400). So, total $1,000 suggested list, plus installation if you don't do it yourself... That's about as much as the 2-DIN dash upgrade, if even you could find the parts to do it, not including the new in-dash unit itself.
I know Nav isn't that critical for most, and given the road noise level, neither is listening to music, but I like to have an in-dash system for both. This is instead of relying on a phone that tends to lock its screen at inconvenient times, and kill off an app spontaneously whenever it feels like it. Using your phone for Nav, for example, means that you can't do other things with the in-dash unit that would divert its audio attention away from the Bluetooth port. For example, I can't hear the turn-by-turn directions from the phone, if the in-dash unit is playing music from FM, Sirius, or the local HDD. I want the AND of features, not the OR of them.
The airflow blockage would only be when the screen is deployed, and I think for simple listening you can do that with the screen stowed. Even so, you still have the side vents (the passenger vent is not that far away), and the car is so air tight that added ventilation may not be all that critical
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So, it's expensive but tempting. Thanks for pointing it out.