I am less convinced that your ship breaking will be fun after the 100th time. And the time it is most likely to break is in combat - and that
might be fun - or deadly. (Though in some ways it
might allow ships to be rebalanced to make smaller ships competitive - if you have to run to the other end of your Corvette to fix the engines then the smaller downtime of an Eagle might be attractive. Unsure.).
Requires loads of new game work (NPC crew etc), and again I'm not sure if the 100th time will be as fun. Much as when people talk about boarding other ships, I'm not sure they're thinking about the hoard of gankers that will try to board them if they try to get to Founders.
Most of your argument is "Would it be fun after 100 times?". But cant you say that about everything? Many people don't like docking after the 100th time, or hyperspace jumping, or shooting at rocks, or pretty much anything the game offers. Having people invade your ship and having to defend it is a gameloop as least as engaging as most of those currently in-game. Whether you personally would enjoy it or not is something else of course.
To me, personally, walking around your ship in Mass Effect didn't get boring. In fact, it was the primary reason you felt like you actually were commander of a large space ship. Especially without VR flying a Corvette is hardly different from flying a Cobra MK IV. Walking through the corridors, seeing crewmembers walking around and such would make me believe a Corvette is not just a Cobra with different stats.
Agree on this - mostly I'm not convinced that things inside your own ship will be other than a time-sink, but the gameplay on other ships is endless and I'd really like it - if we get to wander our own ships as a side-effect then that's fine.
At the end of the day, aren't games in general a time-sink?