I've been thinking and maybe my vote should be moved from 'both' to 'later scenario only'.
As much as it is fun to do aberrations, if we aberrate the whole world it changes into a plain 'fantasy world'.
So if the RoTW is to be aberrated I suggest that it be an option at scenario start 'Aberrate RoTW' On/Off and then mark the .eug file to load differing .inc's dependant upon which option is selected.