NeonZ
Member
SSJ4 is an outstanding design and by far my top favourite in DB. If there was only a way for show producers to know SSJ4 is a fan fave; perhaps a video game statistic. E.g. SSJ4 the most played version of Goku in online battles, where it's available. (I don't know if that's true.)
From a merchandising/marketing point of view, the whole point of a new series is pushing new designs though. There's a reason that DB Kai was a failure in merchandising, but Battle of Gods and Revival F basically relaunched DBZ as a multimedia franchise. Dragonball Kai had high ratings in Japan, but it added nothing, differently from actual new stories. Going out of their way to hype an old design in a new story would just have the same result.
Of course, this intent doesn't really line up with Toriyama's recent minimalist designs and transformations, since more detailed and over the top ones are much more likely to stand out.