Not exactly that crossfeed but made something similar a long while ago but turned it into one with variable pots instead of a few settings.
Played long and hard with it abd thought it might be an answer.
my adventures where written down
HEREIn the end it may have 'helped' with some recordings but I prefer the signal 'straight' in the majority of cases.
At one point I had it set very 'lightly' with just a hint of crossfeed but even though it is an approximation of what happens with speakers it is no more than that.
Room reflections etc. of signals doesn't exactly occur in the same manner and it never allowed me to hear music in front of me or get it out of my head.
It only removed some extreme L and R and positioned it more inside my head.
Not what I was looking for.
Also there were other things like 'blending' of treble L and R which clearly doesn't sound realistic.
When I was a young lad I worked with the guy who built 'the magic organ' which was made famous by Cor Steyn (35 years ago).
Very interesting organ as it had many speakers all producing their own (set) of tones.
It was then that he showed my the difference between electrically mixed signals and acoustically mixed.
exact same signals from the generator but mixed through a console and played on one of the same speakers sounded very different from the two signals each played through their own speakers. Totally different experience.
The same sort of happens with electrically and partially 'blending' as in literally mixing with a small phase shift is what it does simply cannot approach the same effect as real life and acoustical (natural) mixing does.
Some people swear by crossfeed though... I don't.