I think that armoring individual components - in addition to the already present general hull armor - would be a welcome addition. Defensive play is fun, and could use the buff. I'd love the added element of deciding which parts of my ships are more worth protecting. I'd even extend this idea to shields, where you could actively strengthen shielding over certain parts of a ship in the middle of a fight - at the expense of diverting shields from other parts.
Defense needs to be more interactive. It's a common problem in most games - and Aurora seems to be not much of an exception so far - where defense is reduced simply to a flat damage reduction to all attacks without any real way to tweak it or interact with it beyond a flat increase or decrease, and with no defensive decision making during fights. Aurora is a bit ahead of the curve already thanks to the point defense system, where you sometimes have to decide to fire all your PD at once or save some up in case of rapid volleys. Otherwise, defensive decision making (including stealth play) is mostly just about positioning, currently.
I'd suggest something a little different, though. What I'd suggest is having ships be split into different sections - bow, stern, port, starboard, above, and below might be good to start with. Each component from here on out would be placed into a section of the ship rather than some nondescript spot. Different sections could even be bonused for different types of components if we wanted, perhaps with accompanying research tech around ship chassis designs. There might be a tech line that boosts engine power or fuel efficiency for engines placed in a ship's rear section, for instance. Might need a new research branch for this, or you could just put ship chassis/frame stuff under construction/production. This change is important because it opens up a number of what should be (in my opinion) really fun new strategies and tactics.
In addition to the more nuanced ship designs, we could also buff shields by allowing ship captains (the player) to assign stronger shielding to one section of a ship at the expense of another. This could look like a little shield percentage adjuster in the ship screen, or possibly at the task group level, where you can adjust shield distribution by changing percentages over each section of your ship. So, 50% shields over "bow" to protect my guns, and the remaining 50% split across the rest of the ship. These figures could then be adjusted on the fly, perhaps with a small crew-skill-based delay. I'd recommend a button to easily assign a configuration to all ships of the same class. This is awesome because it adds a layer of defensive decision making during combat. I can reinforce shielding over port and starboard (where my guns are), my rear (engines) in case positioning is all-important, or below (life support or whatever else,) or try to evenly protect all of them.
Of course, it also opens up the ability to attempt to target specific sections of a ship. If I want to focus fire on my enemy's rear sections in hopes of knocking out their engines, I can. This also places additional importance on espionage, as the value of stolen ship designs would increase because they'll tell you exactly where to shoot. I'd recommend some sort of accuracy penalty for targeting specific sections, perhaps mitigated with a new type of fire-control tech.
This would also be a stealth buff to boarding parties, as it'd be possible to specifically target enemy engines to disable a ship, rather than just shooting in the general direction and hoping to get lucky.
I think sections would make it a little less complicated for the player than having to individually consider each component, plus it lets us do all of that cool targeting, ship design, and shield management stuff.
Overall I think adding more defensive decision making is one of the better ideas I've heard for Aurora.
With regards to interior/exterior components, I agree that most weaponry, as well as some other components like gas harvesters, hangars, and terraforming modules, should by default exist outside of the armor layer of a ship. To simulate external components, I'd just put an "external" tag on a component and any component with that tag would have a chance to be hit *before* ship section armor is taken into account. The bigger the external component, the more likely it is to be hit instead of armor. If you wanted, you could then add a research line to make some components interior that are normally exterior-only. For instance, with a "Adjustable Missile Tube Armor Plate" tech it'd be possible to remove the external tag from standard or reduced-size missile launchers under the pretext that the tube is placed inside the ship and the ship's armor is placed over it, likely with a sliding plate door of some kind that covers the aperture like a lens cap.