I, as a non-combat role player, don't really see many issues
Sure, a visual bug here and there but that's about it. Chat, usually, isn't THAT terrible either. In fact, I barely notice something has changed. It took me fifteen minutes today to even realize my screen got bugged by a mech.
But at the same time... I just don't really get what seeing four more columns gives you. I just don't see a point.
I also often hear about two issues players present:
1) they don't have a screen that'd support a widescreen
2) they get motion sickness from playing the game on wider screen (I'm not an expert with diseases, I am just mirroring what I heard)
Then also come people who just lack that chat space or simply don't like the larger screen
I believe a good chunk of playerbase would refuse to play with widescreen, and as rurik said, adding a toggle sounds kinda pointless.
Either fully commit to it, or don't at all.