If possible, the effects would simply be rerendered, like in that famous youtube video.
If the recreation of these effects is what's stopping the remaster from happening just upscale them, as it was done in the early seasons of Enterprise, Firefly, and a bunch of other science fiction shows released on Bluray.
However, I think the time-consuming and expensive task of going back to the negatives and recuting the show is the real showstopper.
Wish Netflix would cofinance. They can spend millions of dollars on silly Adam Sandler movies, but not this? I know, I know... The economics aren't there...