Since nobody uses Dizzy in speedruns, I was thinking of a category where you would have to use Dizzy for the entire game. The only rule would be simple - you would have to switch to Dizzy as soon as possible in every world and then stay as Dizzy for the entire rest of the world. What do you guys think?

Personally, I don't see it as good addition. It would be just very slow run compared to other categories making it more like meme walkathon, since Dizzy cannot slide or run, thus is unable to get any better speed. Apart from that, it wouldn't be even true 'Dizzy only' , becasue you have to use Buster at the beginnig of every world anyway. Taking that into account, I suppose it wouldn't be too popular category. We already have 'buster only' for many years and barerly 3 people attempted it. However, if there is enough interest for it and other runners would be for adding Dizzy category, it could be done.