It's the "colorizing Casablanca" discussion.
Honestly, I probably wouldn't be in favor of it as a pipe dream if the difference in resolution wasn't so damn dramatic between live-action shots with and without visual effects in them. If it were just
the space shots that were low-resolution, I don't think I'd consider it such a big deal.
My point is, though, making jokes about "colorizing Casablanca" and replacing the dinky model airplane with some shiny CGI obscures the issue. It's more like proposing to colorize that first version of "The Cage" that kept switching between color and black and white. When Babylon 5 was made, it was by no means intended that the picture should make like the 1950s every time someone fired a gun or looked out a window.
While I, personally, would love the opportunity to give Babylon 5 a new layer of polish, if this actually be came about, I would by no means consider it a waste of time if every effects shot was recreated exactly as it was made in the 1990s, just rendered in high definition.
I've been thinking about doing something like this as an exercise. Maybe I can put together a few images to illustrate the different approaches that could be taken.