Yes, I'd agree that fast slew rate is essential for real low end impact, but don't forget that all of this was forty years ago, and we were working with the best and most reliable big amps of the day.
One of the things that I've experimented with is winding low impedance pickup coils using 7 x 44 ga. Litz wire, and I may just have to try that for the new Mission Control pickups. With that stuff, you get the expected improvement in high frequency response, but there's also a remarkable tightening up of the low end...beautiful extension and punch...due (according to cable guru George Cardas) to the improvement in group delay...basically phase response.
A while back, I rewound a number of classic pickup cores...humbucker, Tele, Strat, P-Bass, J-Bass, Hagstrom BiSonics...and wound them with enough Litz to more or less match the original physical coil sizes. Naturally, the output was low, but with preamping, that was not a major issue. What was really interesting was that the sonic signature of the original pickups was still there...minus the resonant peak and roll-off characteristics within the audio band that you get so obviously with high impedance pickups. Yet still, the Strat pickups sounded different from either Tele neck or bridge, and there was what I call a magnetic signature tone present with all. LCR is not the only defining tone shaping issue with magnetic pickups; neither is pickup aperture. There's a dynamic three dimensional aspect with how the magnetized strings interact with the physical bulk of the coil(s) that helps define a pickup's signature tone.
"The experts" would have you believe that there is no sonic need or use for Litz wire in the audio band; these pickups say differently. It's really interesting getting the limitations of the coils pretty much out of the way. You can always bandwidth limit and/or add in resonances, too.