>Wouldn't most GEV be able to temporarily "jump" out of ground effect for emergencies like that, or at least wouldn't require much change to gain that capability? But that ability wouldn't really make a difference, not without solving all the other issues as well.

Consider these vehicles can travel up to 500 km/h and operate very near to the ground, meaning

1) Vision-obscuring weather like fog or rain

2) A plethora of objects to smack into

3) Very low time to react due to high speed

This is why we generally avoid flying planes this low, unless forced to by circumstances. An example of such circumstances is found in military aviation, in which military aircraft fly very low to the earth to avoid detection (a strategy rendered somewhat less effective modernly due to the invention of light-weight Pulse-Doppler radar). In this case the danger from crashing the plane is judged less than the danger from enemy missiles.

GEVs take this already challenging and dangerous task, which the military only does because they are being shot at, and then make everything that much more difficult by having the vehicle control like a cow.