You can assign a set range in your Midi message and have the encoder /Fader or Button provide the value.
The BC can't access other control values.
You can have multiple encoders with different ranges. You could set up the group buttons so that the top row of 8 encoders has a different range for each of the 4 groups.
Accessing the other controls values and manipulating the value would be very useful, but not possible with the BC alone.
I do this with a PC in between which also allows me to unpack values and sync the BC when a change of patch occurs on the synth.
It wouldn't be much to create a program to use CC values for the range.
Nothing happens until a CC message representing a parameter value arrives and the PC assembles the message and sends it out.
I have started to look at Rasberry Pie computer board as an intermediary.
This could be a cheap solution (about $35 from what I have seen).
But basically I think you are out of luck without extra stuff.
All the best
Royce