Personally, what I like about games like Gamma World where it has the mix of science fiction and fantasy is just the absolute zaniness that comes out of the mixture of the two. When I ran a One-shot centered around pizza delivery men dropping off boxes of Pizza to different villages around a “Famine in Fargo” like area. Ended up working for a Weasel who had wings and a unicorn horn while wearing a pizza uniform.
Something I would like to see more in Science Fantasy is more space centric settings. Like I know there is there is Mars as depicted in the Barsoom series and the Star Wars Galaxy, but it would be cool to see something where you can have planet hopping adventures and space battles without overly intricate rules or anything.
Something else I would like to see are more Power Fantasy Style rules or games, stuff like what you would hear in a power metal album by the likes of Gloryhammer or similar bands. Goofy, strange but absolutely wild and filled with energy.
I might be rambling now but I feel like the genre of Science Fantasy should just go wild.