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.
What I could imagine, as a narrow niche, is a short range regional plane designed to be good at utilizing ground effect on routes that are too short for the "ascend into thinner air" trick to work out and that happen to go over water. Not being seaplanes those wouldn't require sufficiently calm seas for aquatic start and landing. I think that this might be able to occupy an attractive sweet spot between the fuel economy of surface boats and the speed of aircraft in intra-archipelago traffic. Flying slow in ground effect could even be the missing link for creating a niche where electric flying is economically viable. Perhaps a "plug in hybrid" that goes purely electric on short hoops, stays purely electric on longer connections if the sea is sufficiently calm and that can spin up the RX if it is forced to fly the whole distance out of ground effect.
I think that the main economic issue with this concept is that fuel isn't that much of a cost factor in short distance flying, but I might be completely wrong with this.