A mixer with stereo output, with its pan controls, would partially solve this problem.
I have a Tesseract unit Mixer+Master Out
https://www.modulargrid.net/e/tesseract-modular-tex-mix-4-mono-channels
and
https://www.modulargrid.net/e/tesseract-modular-tex-mix-master-section
Good quality-price ratio.
This module has send-return outs, mute switches and it's expandable.