I can provide a perspective on your first point from the gas turbine engine world, so take that for what it's worth in the automotive industry.

While maintainability is a concern, it's only one of many. With regard to placement of the components which fail first, that analysis is done after the designs are very far along. When you learn which ones have the short life, your system is mostly designed.

Doing large changes at that point can be very costly and time consuming. Doing so after you have production-approved components makes it more so. For perspective, I once spent over a year relocating 1 single small component from one part of the engine to another. At one point I had up to 5 other engineers assisting me to meet deadlines.

On to of that, once you have a working production engine, no company wants to spend the time and money to redesign from scratch. You end up designing incremental changes within the overall system design you have, and that limits what you can do.

Feel free to hate me. I'm sure more than one mechanic has put a hit out on me.