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Thanks, you are right 100 % and I appologize I should have made a drawing first.
So I will rewrite my first post as follows.
Now what do you say when the question pops up in an interview?
If you have asymmetric thrust, you will have to counter live engine(s) with rudder to stop the angular motion around the vertical aircraft axis.
Then if you want to fly in a straight line you will have to add up (after steady state condition has been achieved) all components of all aerodynamic and engine forces involved, in the horizontal plane.
If this sum in not zero, no way you will fly in a straight line.
How do you make this sum Zero?
The only thing you can do is to change the physical dimensions of the aircraft and/or bank the aircraft, so you can keep the moments balanced while at the same time change the forces in order to balance them horizontally.
Changing physical dimensions includes in this context "control deflection"
Since in steady state and straight flight the only force on the slip ball is gravity, the ball can be anywhere depending on the amount of bank you need to set all equations to zero.
With straight line I mean straight direction, the plane could still be climbing or descending in a curved line.