Rather mulled this over, and Eldar would not be terribly out of place in the retinue of a radical inquisitor...
Sure, but the actuall issue here is what constitutes a playable retinue.
To use 1e comparison, an Eldar wouldn't feel out of place in an Ascension game, but would stick out like a sore thumb in a core DH game, because Ascension was all about Inquisitors rolling up their sleeves and dealing with things personally, with the aid of their powerful personal retinues, while core DH was about haphazard bands of people gathered by the Inquisitor and sent off on different errands, usually incognito.
The real question is, what vision of the Inquisition and the party's place in it will 2e support.