The in-game diegetic presentation is a cool idea and the mission briefings are nicely setup.
I feel like you could lean a lot harder into the diegetic controls and the feeling of specifically piloting a walking mech as opposed to a wheeled vehicle.
My limited experience with mech piloting games is that they often feel like exceptionally capable tank controls that allow you to rotate your upper half for your view while still needing to track your orientation of your lower half for movement. A tweak like using 'Q' and 'E' for rotating the torso and then 'A' and 'D' allow for strafing movement would really help the feel of mech movement.
As far as leaning into the diegetic controls is concerned, I found it a bit odd that I could rotate my view inside the cockpit while everything that I functionally needed to see was basically in my original view without any rotation required. Beyond that, I wasn't required to click on anything inside the cockpit to interact with them since every player action was bound to a key on the keyboard. Forcing me to click on things to interact with them (like clicking the reload capsule to perform reloads) would really sell the "inside the cockpit" feeling.
I'd suggest toying with increasing the actual display of the outside world to mostly fill the original view rotation (so that it's less painful to squint and focus on) and then moving the radar positionally closer to the player so that they're forced to rotate the camera down (and away from the viewport) in order to get that information.
You could also try things like "arm-mounted" weapons that need to be loaded to the left and right of the player position within the cockpit so the player is then forced to rotate to either side in order to load or otherwise interact with those specific features of their own mech.
Even the compass could be a physical thing that is actually hanging almost directly over the player inside the cockpit so that they're forced to rotate upward in order to check their heading and verify that they're moving towards specific locations for the mission.