The Bad News: There is no magic bullet or "most versatile" EQ and comp. Different strokes and all that...
The Good News: In today's market, analog isn't the only or even best solution for the problem you describe. I can push a clean digital EQ just as far before harshness on the high end as my Sontec.
The Wiess probably comes closest to doing what you want, albeit not necessarily in a single box. The Dyn and LP options are each equally useful, doing things no analog device can dream of. And doing them with a rich, smoothness that will make you weep!
I use the built in EQ of SonicStudioHD for all kinds of things. The higher order filters are amazing for fattening up and warming the most submerged, weak bottoms... A far better solution than maxxbass, and more clear than higher orders on the Sontec.
Between the various digital EQs in my studio, it's very very rare that I feel a need to jump out to analog for air or warmth... I can get it in the digital domain just as easily.
If you work with a lot of analog sources, or high resolution digital, analog processing can be a great and wonderful thing... Sontecs and Manleys never run out of DSP and work/sound the same at every sample rate and bit depth! OTOH if you're working with CD res sources, or project studio mixes, your money would be better spent on great monitoring (not just great speakers, but the whole path, from console to amps to drivers).
It is a myth that "bouncing out" to analog is the best or somehow magical solution for digititus. It's one solution among many, and lately it gets a lot of ink because it's unfamiliar, expensive, and "classic", in a recombinant culture. From our post-modern, cut/paste mash up perspective, we shouldn't forget that this classic gear was created in a culture of more direct creation, where novel sounds and presentation were the norm. A lot of cool gear sounds great because what comes out sounds nothing like what went in, and distorts signals in pleasing ways. We can learn a lot from that approach and apply it to DSP. Recognizing the distortions you like and desire, while avoiding those you don't is possible in digital models. In other words, you can model just the opto sensor, without the transformers, or vice versa, without hacking the hardware.
As for the gear you mention... I love the Millenia NSEQ, and thought it would be a great compliment for my Sontec, but at the end of the day didn't buy it because it reminded me most of a great digital eq, which I already have. I don't think I would want one for my sole analog EQ because it's so colorless and clean... it has almost no signature, almost like LP. The Massive Passive goes the other way: All color, all the time. A Sontec or GML provides a better balance: they can be very smooth and colorless or quite aggressive and rich at higher Qs and boosts. Maybe IBIS is like this? Others who've used it will chime in
The STC-8 might well be the piece closest to an ideal. It's clean and interesting, and should generally do more good than harm. I love old LA-series opto comps, but they're very limited by design. An STC-8 would be useful for many things... it would be at home between an analog tape deck and ADC during a transfer, trimming off peaks in an elegant, good sounding way, and equally useful as a go-louder step in a chain.
-d-