I'd say DHs need more race representation, given they are available only for one race per faction. The problem is in class animation I guess, some of them are actually tied to metamorphosis visuals, which are based on elves. Adding the class to non elf race means they would need to create whole new set of animations, which is way more then creating new druid forms or shaman totems. Given class skins, it could not be that huge issue, since they work on premise of altering class visuals in the first place.
So yes. Class skins could indeed open up interesting class/race combos across all races. As for void elves, Void knights and riftblades seem as cool concepts. I can also imagine Astromancer skin for mages and Voidcaller skin for warlocks (replacing demons for void beings/faceless and altering fire spells to Void). So many possibilites. So many flavors