Are you wanting the engine compartment to cool faster after stopping or trying to keep it cooler during driving?

The impact of removing the tray could be different in these scenarios.

During driving this might have an impact on the air flow through the radiators and turbo intercoolers. (might change the back pressure in the engine compartment not necessarily in a good way). Would be an interesting topic to research. Probably only be noticeable under very high engine loads.

 

It's very likely that Porsche engineers torture tested your car's design in condition far worse than you experience.

 

My main concern is time-at-temperature. More time degrades organic materials like rubber and seals ( ac compressor seal for example). So anything that can be done to reduce the time at high temperatures will help. But you may be right that all of this is well considered for all climates but I have seen premature failure of plastic devices that contain check valves and other plastic parts in an engine compartment that had an under tray (not a Porsche). May chat with the Porsche techs. It could mess up some other airflow. Not sure.

 

Short term (few days) I would run without lower engine splash shield. Ling term, would likely put it on, since small clearance and debris dknt mix well. Lots of stuff that can get damaged then you end up paying 3x the price and time.
engine does run hot, but such is Porsche life.