Maybe also a cool thing to add it as part of param eq. Like mono sum below 100hz with vinyl masters:
https://gearspace.com/board/mastering-forum/1275202-summing-low-frequencies-mono-vinyl.html
I think narrowing is kinda required, "thanks" to nearfield monitors the stereo width varies wildly and if it's a decent M/S mix it should stand narrowing without issue. Think of it as rudimentary crossfeed.
I find widen kinda useless in practice.