These thought experiments are fun.
Angle of attack is the angle between the wing’s chord line and relative wind.
Of course, having momentum or inertia, the aircraft isn’t instantly going to change direction, even when applying pitch up, and hence AoA increases. The momentum changes with mass and speed, so I would say mass is a major important factor here as well.
Correct me if I’m wrong, but in your 1G setup:
Let’s say Airspeed is constant, altitude is being kept level, and the aircraft is experiencing 1G such that it would correspond to a certain Angle of Attack. Well… that is because at a certain airspeed, with the correct angle of attack, you are producing lift that equals the weight of the aircraft, no? That’s why the aircraft is kept at constant altitude.
So factoring weight: If weight increases, then the altitude would drop at the same AoA/Speed as before. So either: A Speed must increase, or B, AoA must increase. For either to work, additional thrust is needed to maintain situation A or B.
As others have said, altitude isn’t really important in aerodynamics, it’s more specifically atmospheric density, which changes with pressure, humidity, temperature etc.
I’m no engineer, only a mortal mechanic so I only know the basics.
Good luck figuring it out though!