Mixing
I always recommend the same, I have it and I am very happy.
https://www.modulargrid.net/e/tesseract-modular-tex-mix-master-section
https://www.modulargrid.net/e/tesseract-modular-tex-mix-4-mono-channels
There are 4 mono channels with CV, send and return, mutes and pan. They are also chainable, so you can grow using the same output. 4 channels plus master are 18HP, but the ergonomics are quite good, at least for me. The price-quality ratio is great.
-- ferranadsr

Thanks… the Tex Mix definitely isn't for me. I had one about a year ago, it was just too cramped and eventually got returned as it had a scratchy pot

I'll have a think about the other ideas, the only way the Pico DSP stays is if it can live of the right hand side of the case - it's just too small an fiddly otherwise