That could work. To be honest, short of racism, race-gating does not make sense to me. But I guess I should withhold judgment until I see how they've worked it out. (Though I'm currently seriously short of caring.)
Honestly, race-gating because of possible racism makes me uncomfortable. Cullen's situation with mages is nuanced and not a simple matter... racism... is just racism. It would definitely affect how I would view 'em.
Then again, this 'story reasons' might not involve racism at all. Examples:
Vivienne keeping her politics in mind.
Solas wanting to be able to share the Fade and his lucid dreaming with his LI.