Call me a romantic, but I think of Category Extensions not just as a home for extra leaderboards, but as a place where we can foster all the fun aspects of Pokémon speedrunning. In my ideal world, Category Extensions will serve to better the community in many different fashions. Here are just a handful of ideas of what I think Category Extensions could (and should) be:
We'll have a handful of shorter, simpler, and less serious categories mixed in with the others. We should aspire to make it easier to capture potential new runners from an audience who might otherwise be hesitant about getting into Pokémon speedrunning. Some examples: Beat Lance (for a shorter run than Glitchless), Manipless and Gold Any% No Save Corruption (for more accessible categories for a first Pokémon run). We can add other category ideas along these lines, as they come up.
Category extensions allow us to explore the games we love in ways the official leaderboards don't allow for, free of judgment. Do you want to use a different main poke (Alt Main Pokes), use a bunch of different Pokémon (Baton Pass), catch all of the Pokémon (Catch 'Em All), or just relive getting rekt at Battle Tower like you did as a kid (er, that might just be me)? Categories that add freshness and variety and provide new ways to make us nostalgic for these games are perfect fits for Category Extensions.
Routing is an extremely enjoyable aspect to many involved in Pokémon speedrunning, but one that's at a stale point for a lot of official leaderboard categories. Category Extensions provide a massive new terrain for routing creativity and fun. Any category with real, appreciable, original routing is something that will have a place here. (The fun is already getting started: Alt Main Pokes has taken off recently, in large part due to Exarion's Fastest Pokemon Project for Gens 1-3.)
Sometimes the original games just aren't enough for the truly vivid imaginations in our community. What if we had access to different starters? What if the Rocket segments were removed? What if every trainer was a spinner? Category Extensions provide a place where we can answer these types of deep & burning Pokémon speedrunning hypotheticals.
"Minihacks" had their heyday from 2014-2016, with fun and awful ideas alike (see the original PSR forum thread). It would bring me great joy if we happen to re-energize the romhacking segment of the community and keep them busy with new ideas.
Meme categories are most welcome, and we will bring memes back to the people. Category Extensions are a paradise for those who treat memeing just as competitively as they treat Pokémon speedrunning. Who is the best at coming up with memey categories? What is the memeiest category we can design? Can we beat the word meme into the ground and deprive it of all meaning? (Most likely, yes; yes we can.)
Some random examples of meme categories that would be welcomed with open arms: "Nintendo Power%" (see here), "Poison a Nidoran" (spoilers: it involves Twineedle), "Obtain L69 Poke". Have other ideas? Go ahead, show just how big you can meme.