Yeah, if all else fails, just use the input transformer.
Attached is a preset that turns CC21 into CC11. Extract it into your “AppData\Roaming\Steinberg\Cubase\Presets\Input Transformer\Controller Filtering” folder and change the controller numbers to whatever.
The downside is that you only get 4 of them at any one time.
CC21 is CC11 Preset.zip (558 Bytes)