Engineering Students here - any tips?

I'm an engineering student (mechatronics) that did a 3-year apprenticeship a few years ago, so I roughly know how things are done, but that's about it.
For years I've always wanted to build my own CNC lathe, and am now starting to plan for it, however I am unsure whether or not the "ideal" tolerances are actually even slightly achievable using a regular lathe (that I have access to) or not (there is a very small change I could grind it on the lathe, but I doubt it)

I am also wondering whether or not the surface feature callouts actually make sense this way (concentricity and runout on the two bearing seats)

Third question would be a material of choice - I was originally planning to use 42CrMo4 (AISI: 4140) but it turns out it's pretty expensive in the diameter needed, would something like C45 (AISI: 1045) be acceptable?

I'd greatly appreciate some thoughts and comments on the part (main spindle shaft) and whether or not I have to make some changes to make my life easier - thanks!