Heck yes back then everyone was trying quadraphonic cross pollination. Even Sansui had a
patent for a carrier disc system like CD-4. The goal was to combine the qualities of matrix base-band decoding with high frequency separation enhancement. Sounds just like CD-4 but I think the consumer end product would be a simple QS decoder with the carrier signals doing the enhancement.
Even Sony had developed a Variomatrix kind of ch blending to increase separation for either QS or SQ. I can't find the patent on line but perhaps someone else can: 3,786,193.
I agree with you on both your positions of SQ/QS. I bought SQ partly because I knew hardware was in development & even with basic to more advanced I would get the wide front L/R I was used to in stereo. I was amazed when I first heard QS Variomatrix play back stereo. Incredibly better than trying to squeeze something anything out of an SQ logic decoder
And there lies the irony: SQ was the most compatible encode system for producing stereo quality sound & QS was the best for playing stereo to decoded surround!.