got it! i´ve been enlightened.
even though i didn´t manage to provide a parameter feedback for the bcr, i did find a way to work around my problem:
the trick was to use the generic surface plugin. with it there are 2 possibilities to work efficiently with the bcr.
1. to use an absolute controller:
first you have to set the bcr controllers like this:
[type: cc, ch: *user*, parameter: *user*,
val 1: 0, val 2: 127, mode: absolute (abs)]
after that you can assign the desired parameters to a knb on bcr in generic surface (press F1 for help for instructions) by using the "learn" button.
if you move the assinged knob on the bcr now, the onscreen fader won´t move until the bcr-knob reaches the same level as the onscreen fader.
2. to use a relative controller:
set the controllers like this:
[type: cc, ch: *user*, parameter: *user*;
var 1: 64, var 2: 65, mode: relative 3 (rel3)]
then assign the parameters in generic surface like above.
now the knob on the bcr will continue the level of the onscreen fader, whatever position the onscreen fader is.
but when this possibilty is used, the LED cricle is useless. technically you can turn it off (using the remaining two editing knobs without a white label).
either way, the onscreen faders won´t "jump", when the onscreen level doesn´t match the bcr-knob level, which can be pretty disturbing on volume. that was technically my basic problem.
plus the setting can be used on any project when generic surface plug in is used. so you don´t have to assign the knobs manually for every single project.
and, at last, i don´t need to save the knob values on the bcr for different projects in seperat presets.