I think I take it to another direction.
If I add the Doepfer A-138S (Stereo) mixer with panning, I can use that also for other puposes.
But I can mix the 2 Return signals hard left and right, and add 1 or 2 other signals the way I like (left/middle or right).
That seems to be more flexible then my original wish.
https://www.modulargrid.net/e/doepfer-a-138sv
Maybe an even better alternative is the Make Noise XPAN.
But at the moment I do not think I have the budget for it.
The idea behind it is a little better for me, and I like the Aux in for decentralized mixing.
https://www.modulargrid.net/e/make-noise-x-pan
So for now I think the next purchase is the Doepfer A-138S, then I can concentrate myself on other area's in the rack.
Maybe it will bring some noise, but for now it will be enough.