I wouldn't have a problem with someone using gors as marauders. I actually want to pick some gors up just for that reason.
If and when I ever go to a more monstrous theme, I would use gors as marauders, minotaurs as ogres, cold one/black orc conversion for dragon ogres, and shaggy as shaggy (any suggestions for a plastic conversion).
I might even go as far as using gors/marauder horses (like centigors) as marauding centigors (marauder horsemen) or bestigor bodies and knight horses to convert into centigor/chaos knights. I think I confused myself there.
Granted if I go that far, why not just play beastmen. Maybe it is a way of using some cool beastmen models without having to field a huge amount of models.