I know this is a niche interest, but I write and play solo, instrumental guitar, with the QC as my near-perfect setup. I have long looked at ways to create a Quadrophonic ‘live’ rig. Using the four outputs on QC, each feeding a separate HeadRush FRFR monitor, I see no reason why in a small venue the four monitors arrayed facing into the room in a circle, couldn’t work in a very immersive way - if the QC were configured to create a ‘surround sound’ experience for the listeners within the circle. For example, a four-tap delay, with the facility to send each ‘tap’ to a different monitor. You could have a delay/echo moving around the four monitors creating a perception of motion for the listener. If a block were designed to enable a ‘four tap’ output - other effects could be adapted along the same lines. Imagine a quadrophonic Leslie, or phaser moving around you as you play… Quad rigs have been around for decades (Pink Floyd) but with modern tech like the QC, we should be able to make it work on a micro scale - and move on from the default ‘Stereo’ systems we are so used to. This would be incredible - especially for solo artists who play instrumentals using direct out to FRFR/PA (If Mics/vocals etc were involved the feedback issues would likely be a problem) I can’t see why a dedicated ‘Quad/Surround’ block wouldn’t work - it could be incredible.
Actually quite a nice idea! 
I used to be a live sound engineer a few years back, and at one point was running a stage at a festival where Amon Tobin was due to play a set in full quadrophonic.
We had the PA for that stage set up that way for the full festival just for him - four stacks arranged in a square, two either side of the stage and two at the back facing the stage.
Took us a lot of time to get it set up correctly, and we had loads of complaints about the sound throughout the weekend, because depending on the frequencies playing and where you stood, you could either get zero bass, or so much bass you couldn’t hear anything else.
In short, it was a nightmare, and to top it off, the promoter messed up and Amon Tobin didn’t even know it was set up that way for him, so didn’t bring his quadrophonic equipment.
Anyway, TLDR - no venue will ever have it, and if they actually do, to get the most out of it, you have to be stood in exactly the right spot, otherwise it sounds wrong or even awful.
To add to that, you can actually do this already, just not in one block.
Create two signal paths, both in stereo with stereo delays, then get the timing and panning right.
Yes - good points. I am experimenting with the stereo delay pair just as you suggest - but with a Strymon Timeline after the QC to give me more options (I love the Grit control for darker ambient ‘noise’) I know Quadrophonic is very tricky - I doubt it can be done in a band context, but maybe with just a guitar, you could get a worthwhile Cinema type sound with some success. I saw Kate Bush on her residency at Hammersmith a few years ago, and there were small PA speakers at the sides and back of the room which created some spine tingling moments - not in terms of the overall band sound, but for some specific surround sound moments. With the QC (or one of the other top end modellers) we ought to be able to push the boundaries’. I play cinematic, quite ambient stuff (with tunes - not just soundscapes) and I think I’m onto something with this micro surround idea - it won’t be perfect or work in every scenario, but for specific venues it might just add something special. It would need to be targeted - just delays or modulation (Leslie?) - if everything was swirling around it would soon turn into some psychedelic flashback and make everybody sea-sick 