Yes; milling is fiddly but because the forces are so low (and you can reduce the mechanical accuracy needed with depth probing), it's possible to do reliable pc

Yes; milling is fiddly but because the forces are so low (and you can reduce the mechanical accuracy needed with depth probing), it's possible to do reliable pcb milling for similar to cost of decent fdm printer. People are doing this today but everything is jank, nobody's repackaged it with prusa-like reliability at hobbyist prices AFAIK. Ideally if you could get v thin copperclad with a substrate that doesn't produce toxic dust, with the right software and jigs you could produce "basic" multilayer boards(1) with 1 "pin aligned" flip and a few manual tool changes for drilling etc. It all seems possible today but has never been packaged nicely and made cheap, I suspect because the market is not big enough. (1) one big issue... the boards produced would be vastly inferior to "real" multilayer boards, would mainly be usable at low frequency, you could get complex layout / routing but they'd suck at high frequency and in several other ways. You would need to relayout / redesign to target a "real" process, which is somewhat undesirable for prototyping.