I highly doubt Glauca was supposed to be Clarus. There is another face that we see in the 2013 CG faces that we never saw again, people often mistook this face for Cor but it ain't.
Here's Cor's face just for comparison.
Something common I've seen people say is that this unknown man could have been the original Drautos, before they had a mocap actor facial scanned for his face. I can see where they are coming from too, though I'm not sure if the character of Drautos in particular was ever a part of FFXV prior to Kingsglaive becoming a thing. So if this unknown man was supposed to be Drautos, we'll probably never know.
The only character with short dark brown hair with blueish eyes we ever saw prior to XV was the Driver from the 2011 Versus trailer, the one heard saying "Noctis Ouji" repeatedly in the trailer, who Nomura had confirmed was originally voiced by Hiroki Touchi, but that Hiroki Touchi later became Cor's voice actor by 2013 and Nomura said that the Driver now had a different VA. Maybe the unknown man from 2013 CG face renders was a modified version of this man, who BTW is also wearing Roen clothes, as indicated by the Roen skull on his vest.
I always thought it was odd that this supposed innocuous man was shown almost as much times in this scene as Noctis was, and this is pretty baseless on my part here but what if this dude was Glauca, or an original incarnation of "Drautos"?
After Noctis mentions that the Niflheim ships heading to the Citadel look as if it's gonna be taken over the Driver looks at Noctis then shifts his gaze in the opposite direction and purses his lips and "swallows" his lips, and then laughs Noctis's comments off, in terms of body language what he did on his mouth is a sign of hiding the truth, or suppressing information, sort of like how crossing your arms means someone is being defensive. If this man was actually Glauca, wouldn't he know about the incoming invasion and intentions of Niflheim? And when Noctis made that comment the body language the gives off falls more inline with someone hiding or suppressing the truth, as if he does know the truth and is purposely trying to hide it from Noctis by laughing it off.
This man also waves to some Lucis royal guards we can see standing by the gate, at first I thought they were saluting because Noctis was in the car, but what if they were saluting because this Driver was actually himself someone in Lucis upper military? He's driving Noctis around so back in 2011 people assumed he must be low on the ranking and just a driver, but Cor drove Regis around and he is general of the Crownsguard, and even in Kingsglaive Drautos drives around Noctis's car, so what if this guy was someone important within the Lucis military given that he is the one driving Noctis around?
I wonder if Drautos being the one driving around Noctis's car is in anyway a nod, assuming the 2011 Driver was the original "Drautos". Even during this scene Drautos is hiding information and pretending to be ignorant about what's really going on to Nyx.
And in the 2011 trailer when driving off the Royal Guards salute the driver as a show of respect.
These guards from the 2011 trailer are still used as we see them a lot in Kingsglaive and they even made a whole named character as one.
And in Kingsglaive there's also this scene where a Niflheim person is talking off to that Royal Guard who when Drautos comes in the scene fixes his posture and stands up straight as a sign of respect.
It's not really much to go off of but at the very least I think they are nods.