I really like the welch labs series on imaginary numbers which covers the first part of what you talk about -- leveling up the notion of what a complex number is. Though his focus was more on solving simple equations with no real roots, but really detailing how/what is really going on.
It is a great precursor to then thinking about quaternions
It is a great precursor to then thinking about quaternions
https://www.youtube.com/watch?v=T647CGsuOVU&list=PLiaHhY2iBX...