Time for Steinberg to bring out a new Cubase controller I think. CC121 seems increasingly dated / limited and 10.5 doesnt seem to play too nice with it.
How about then, something keeping the essence of CC121 but taking a step towards the console 1 model. So motorised fader, transport, pan, function buttons (8 please, not 4), inspector buttons, but also a section that gives a vertical strip of 4 or 5 control knobs which smart-swaps to each section of the channel strip once its selected (or by a L-R selector on the unit). Same 4 or 5 knobs could be used for each module of the strip via a selector. Also - allow it to be used with our own custom channel strips made from 3rd party VSTs which map to these knobs automatically if set up once by user (kinda like building an expression map. Would be handy if we don’t want to use the cubase channel strip (ie could have a strip made up of Brainworx -->Slate -->NI–>Softtube and 4 parameters from each could be assigned to the nkobs on the control surface. Would be amazing to just drag and drop favourite channel strip chains onto tracks and have a control unit automatically pick up the right controls for it as you select through tracks in your project. The vertical knobs on the unit would then each need a little LED display strip below each knob that changes to show the right user defined parameter text when each tracks channel strip is selected (kinda like the LED displays under the knobs of the last version of NI Kontrol keyboards)
Make it look pretty, use less plasticky buttons and knobs, and use layout space more sensibly (the whole right hand section and EQ section on CC121 are a somewhat dated of space I reckon - could be implemented way better.) You’d have me throwing my wallet at you. In a happy way, not an angry way.