Here, this is right on the dime. Solution for most alignment issues can be solved with cuff alignment. Fine tuning with shimming the bases. I would not stuff my boots with foam but high end boots usually have cuff alignment adjustment.
I don't agree with this. Most issues can be improved with cuff alignment, but not solved. The best solution is most often a combination of insole posting, canting and cuff alignment, and that is just the lateral..
Didn't you find your best alignment when you tweaked both canting and cuff alignment?
I think the problem with simple solutions is that they don't solve the real problem. If you tweak your boots by looking at the knee alignment when standing flat in your boots you have tried to solve just that, standing flat. In reality you spend most of your real ski-time on the edges.
So for example, balancing on edge, the canting changes only the angle between the ski and the snow, in other words how agressive they are. However if you are standing flat canting pushes the knees outwards. In general it is not possible to only cant the boots so that you have even pressure when standing flat, the right level of agressiveness AND a good-looking knee alignment.
By tweaking multiple parameters you may get closer, but most often you need to compromise, for example a racer would probably prioritize agressivness and flat pressure but may accept some A or O frame.