I think the fact that the value of the 'E' in the offshore role is debatable or not currently reliable is only valid up to a point. Until such time that every mobile vessel has some form of real time position update that EGPWS can use to update itself, it is bound to have small risk of missing obstacles. Used in conjunction with RADAR the risk must be considered very small though, and by definition, no worse than current practice.
I think the thrust of effort must be towards refining the classic GPWS modes. I fear that in an attempt to avoid nuisance warnings, and the syndrom of them becoming normal and therefore ignored, the thresholds have been set unrealistically high/low (no pun intended!) leading to insufficient protection over water. Rates of descent, for instance, can be artificially generated by rising ground. Over water they have to be actual RoD, which means that only in extreme circumstances will a threshold be breached.
Maybe, instead of a LOW ALT mode, there could be an Offshore mode?