Speed buttons are okay. I don't mind them for any kind of gameplay, buuut sometimes in general they can make one skip a few things. ...Especially Let's Players. I keep up with MunchingOrange and he uses the speed button when available, resulting in some rather preventable deaths. Now, I ain't about to sit here and say that he's the best Pokemon player in the world-- he can be rather frustrating to watch, in fact. Still, sometimes that even happens on grindy sections, so it's not always wholly his fault. I find that I also can have a tendency of losing my focus when grinding and-- whoops! Pokemon drops faint for some reason I couldn't see. Annnd now I have to drag out my next Pokemon that might be weak to this Trainer. ...Whoops.
In general though, I think it's a good idea. Just... be mindful when playing. Which is a given, but a hard rule to actually implement.
I would worry about it being implemented in Pokemon Essentials, though. I could be completely out of the loop-- actually, I am-- but isn't that hard to implement? Didn't someone try that several years ago and it didn't work as well...? And even if it does, a Fangame can lag-- a lot, sometimes. It depends, really, on a LOT of key factors (and that's a whole other bag of worms people can't 100% figure out) but yeah. *Shrugs*