Either making it in 1996 instead of GT or not doing anything different to at all.
At the moment, it's an acceptable piece that can still slot between Z and GT if you so want it to. Making a GT sequel would have just devolved into the silliness seen in variations of the AF fan manga. Toriyama wrote a story that he deemed "finished" in 1995. Toei concluded that ending in 1997. Doing anything other than Super - unless it was a one-off special like Goku Jr - just would not be a sensible move, and I doubt Toriyama would have been interested in telling the story.
The fact that he's involved (to some degree) in Super at the moment, and wrote the two movies, indicates that he at least wanted to write this as a sequel rather than GT.
Don't get me wrong: I'd definitely rather watch GT than Super, but as best as we can tell from the information, Toriyama wasn't overly keen on being involved with GT. I don't think continuing that story that his heart isn't in does the fans any service, let alone the guy who is responsible for birthing Dragon Ball.