Hey, I'm a game enthusiast like most if not all of you, and I've been watching speedruns for well over a couple of years (shoutout to Werster !!) and I've noticed that all I've seen is Mudkip as a starter. Besides the obvious reason Mudkip being the best starter for speedrunning, is there even a speedrunner that has done a Pokemon Ruby/Sapphire/Emerald Speedrun with Treeko as a starter?

It would be very interesting to see different strats and routes used to compensate the poor starter choice !

I hope I get a response and a video or stream of someone interested in this ! Possibly a new category ?

You should always ask game related questions in the game's forum. In your case http://www.speedrun.com/pkmnemerald/forum Welcome and good luck with future runs :)

There must have been someone who's done at least a challenge which requires a different starter for a speedrun, there are many more categories such as randomizers and such, maybe not official but they're still done and I've seen many done across Twitch from different speedrunners. Different strats and routes are being worked at this point much more than before, especially with RTA now being a thing but I don't think Mudkip as a starter will change for those games. You can try to contact Pokemon RSE speedrunners though and see what their response will be :)