some of these building games feel more like modeling programs than lego, and that is kind of a problem. some procedural parts are a good idea, like to-spec tanks, fairings, and wings.
as for null rot i think it should kill rotation and have a separate attitude hold mode that will maintain the current attitude but will allow you to make changes (to the setpoint rather than controlling the thrusters directly). perhaps marking the setpoint on the nav ball for display purposes. i never really liked having to ride the f key in ksp though to make sure it stops where i want it, i felt like i was always fighting the control system.
this is where i like the idea of different thruster firing modes via modifier keys. like a mode where if you hold alt, you can fire a thruster with one of the controls, and an equal and opposite burn duration is then performed when alt is released. we can keep shift/caps as the vernier mode and maybe control key will allow precisely timed pulses.