It's not about
Aria entering the safe house specifically, but the MC not even attempting to use any leverage he may have. If she's already going to be around,
then get her under the command structure as a special agent, have her do debriefs, link her to her Lady so they both fly or fall together, put her to work and see if she follows instructions (for now) or immediately goes off. These are, just off the top of the head, reasonable ways of testing that faction and what their priorities are. There are steps between being completely passive and trying to kill your own team/assets.
And, as you said, personal safety isn't his highest priority, but all these little displays, subterfuges, and posturings distract from the mission, muddy the waters, and slow the investigation. The lack of any preparation or dealing with these long-term problems that are coming from
inside the team, shows poor leadership and how ineffective the MC is as an officer. This isn't even platoon size (though the egos might make up the difference), and he doesn't have to deal with them all being green recruits, but the MC has done nothing to forge these folk into a unit, least of all one that actually respect him, the mission, or be able to work effectively to their goals without undercutting him, the unit, each other, and the mission.
It's a shame, because I can see the sparks of something interesting in the MC, like spotting the feint in the sparring battle, but then that seems to disappear elsewhere (especially anything nearing Lady S.). I don't think the story or MC are bad, just that the balance seems out of wack and it is doing the overall project harm. I wasn't expecting hyper-competent power-fantasy porn, just a protagonist that actually takes some action on their own. Just tone down the passive/reactive aspect by 5-15% and it'd improve things greatly.
Also, I'll probably keep harping on it, anyone who kills their own team (
Grace, and probably
the rebels with Dizzy/Rose) without first exhausting every other option is an untrustworthy piece of shit that should be kept away whenever possible, never considered as a potential ally, and if possible, cut out of any operational calculation completely. An infantry officer, a combat, active war, infantry officer, should not be blase
about having someone join the team that frags their own side, even if they splurged for a slightly fancier frag. Hopefully MC is holding his cards close and will play them
to drop Lady S. off the side of a cliff after squeezing as much intel/resources as possible, because if there is one thing consistent from Sparta, to WWII, to any military conflict I've heard of, you live and die by, and for, those standing next to you when blood starts to spill. You don't abandon them or push them into enemy fire just for convenience. Command already does that kind of shit, you can't have it next to you on the line as well. It's fine to make
Lady S. the villain here, but the MC has to call it out at some point or it ruins his character. Even the non-military folk should be unnerved by that.
I'm engaged with the story, it's interesting and I want to see more, but it's also irksome as hell in some ways. Look forward to seeing what's next, or if tweaks revise some elements of it.