Raul,
I have no dog in this fight, but I would point out two things in response to your long post:
(1) In part, It is certainly possible that integrated designs went away back in the 80s mostly because phono itself was on the wane and the latest and greatest tonearms of those days tended NOT to have removable headshells, which would render such integrated cartridge designs unusable by their target audience of high-end aficionados.
(2) It's rather amusing that intrinsic to your argument is the notion that 30-year-old cartridges and the like are "old fashioned" since this is a contradiction of your original mantra (which states in part that attention to quality of design and construction was at a higher level in "those days" compared to the present). I would posit that the observation that rebuilding vintage cartridges typically results in an improvement in performance could as well be due to deterioration of suspensions with time (applicable even to NOS samples) and/or to abuse of the original construct by previous owners of used samples, as to true benefits of the rebuild. For a given cartridge, we can never know the truth in that regard. There is also the fact that after a rebuild one "expects" an improvement; this causes a subconscious bias in favor of hearing an improvement. None of us are immune to that bias. This is why serious science demands double-blind, controlled studies as a qualification for publishing.
It's true that having a choice of headshell, wires, screws, torque on the screws, etc, does allow much more freedom to "voice" a cartridge. Perhaps in your hands, this is a big advantage. For most of the rest of us, we are taking a complete shot in the dark. We could be missing what a given cartridge may have to offer by making bad choices. At least with an integrated design cartridge, one can assume that those variables are not in the equation, and one can hope that the engineers who designed the product made good choices so as to maximize the performance of their product.
I'm just saying'