This is probably an unpopular opinion, but I actually liked the Fed troopers in 3. They made the world feel bigger, more "real", and never really interrupted gameplay. I also liked how they were characterized. They had little to say, were quick and professional. They felt how futuristic sci-fi soldiers should feel. I remember early on in the game there's a trooper you can talk to who's fixing a control panel or something. I don't remember the exact line but it was something along the lines of "Hey Samus Aran, I get you're a big deal and all, but as you can clearly see I'm busy. So stop bothering me." It was a real minor thing but I really liked that interaction, because it makes perfect sense. We're in an active war zone, we all got shit to do stop trying to make small talk. I also liked how the troopers weren't really all that impressed with Samus either. Which again makes sense. These guys have seen shape shifting aliens, giant mechs and a cyborg dragon all in the span of one day, Samus is tame in comparison.