That's kind of my point. They're never really shown in-depth, and I'm sure that there are going to be at least a few issues that crop up from it. For example, the regular soldiers are pretty much nothing but cannon fodder. They can barely hurt the Neuroi with conventional weapons, so they're stuck simply holding the line until the cavalry can swoop in and save the day. No one likes feeling useless, particularly when their own lives are on the line, and I'm sure if you compared number of deaths between Witches and soldiers, you'd have a lot of dead soldiers compared to Witches. There's also the fact that Witches can be as young as 13 years old, so adults, who can't do anything but throw themselves at an invincible enemy, are being saved by children, which is probably a massive hit to a person's ego, and there are probably a number of other reasons for there to be issues, such as a Witch's perception of war, which is possibly more lighthearted than a regular soldier's seeing as how Witches suffer much less losses and, in general, have an actual chance of winning their engagements.
I mean, yea, they wouldn't have any issues working in tandem with Witches, after all, they're one of the few things that can kill a Neuroi, but I'm sure they'll have gripes and tension that they don't say to a Witch's face. After all, do you really wanna badtalk a girl who can carry around machineguns one-handed?
I understand if this isn't something you want to do, I simply want to know if this is something I could play.