Ok, that’s the first attempt:
Center Removal, Isolation and more
The tool is - as it is - not specialized for center isolation (including echo cancelling and such stuff), but it attenuates at least by 3 dB (near the center).
This value increases rapidly towards the sides.
You can control which portion of the stereo field should be attenuated the most y choosing “Isolate Center (inverted)” and applying it on a duplicated track.
If you change the gain of the original or the copy, the focus that cancels some part moves gradually sidewards.
Happy experimenting.