It's an interesting idea...but IMO puts the player in a bind in terms of RP.
If I had to pick a spirit to embody my Lavellan, it would totally be Hope. But what about Assquisitor? What about my Adaar, who IMO embodies Valor much better than Hope? It kind of forces the player into a particular sort of PC in order to make sense.
Just like Wisdom can be corrupted to Pride, Purpose to Desire, why can't Hope be corrupted, or at least made to never reach its potential?
After all, one of the first things Solas asks Inquisitors in their disapproval scene is "Are you blissfully unaware or, deep inside, is some part of you banging on the walls, screaming?"
That itself suggests that even Assquisitors may posses a quality that fascinates Solas, even if Quizzies themselves fail to impress him.
If you look at it that way, not only it makes perfect sense in the world of Thedas, it also provides great RP opportunities 
It's like Solas said to Cole: "While the world may exert a pull in one direction or another, the choice is ultimately yours". And considering that it's largely hinted that most living, sentient beings are 'spirits made flesh', it's appropriate for them to follow that path as well, even if they don't exactly end up to be as pure or as twisted as spirits and demons.
It also makes sense for Solas to be absolutely baffled by approved Quizzies - it must be a true mystery (of not a downright miracle) for him how come approved Inquisitors can retain their 'purity' in a world as bleak and corrupted as Thedas and would be an appropriate impulse to re-evaluate or at least consider changing his stance on things.