This is the entire reason I wanted to make an Alex in ME3 armor. Because a tender moment on the battlefield looks ridiculous with Alex in his hoodie and Shepard in her armor and because no one has been able to port Alex's virus armor form from the game to XNALara. Even if there was a model I would still want his head to be visible... so I made my own!
I like to think that Alex makes his armor take the form of normal human armor so he can be distinguished from the reaper forces on the battlefield.
I also think that Shepard would make Alex stay back and defend the base in the end because they need his abilities more than she does.... up until Harby shows up then the shit completely hits the fan.
Content (c) Bioware & Activision