@nicktoonhero  
Well, there’s this Sir Connery guy from the official Sonic comics, but he didn’t look much like a “Sonic-character” to me. Though, that’s mostly the artist for that issue’s fault. (James Fry) He never really draw the characters very Sonic-y, so I don’t know how he’d look in Yardley, Ben Bates’, or other modern Sonic comic artists more “Sonic-y” ways they draw. (They seem to be trying to keep the art in the comics nowadays more consistent with the Sega game style. Some fans prefer it that way, while some don’t.)
 
Also, the horse dude is dead now, so it’s kinda a moot point. (He didn’t have a huge role in the series anyways, only appearing in a few issues.)
 
Still, I guess we can gather that horse-animal-people are taller then Sonic, and some other Mobians. (Perhaps as tall as a human, or taller.)  
So considering “ponies” are basically “small chubby horses,” then it can be assumed if the Mane 6 became Mobians, then they would probably have “short Mobian proportions,” like Sonic, Knuckles, Amy, Sally, ect. and be smaller then a human perhaps.  
So I think that “look” kinda suits them in fanart like this one.

@Beau Skunky  
Makes me wonder what do horses look like in Sonic’s world.

@Vocal  
Yeah, you keep telling yourself that…

This one is not creepy.  
I do not need an adult.

This is good, I like it, eyes are on the creepy side by not bad overall.

It’s nice to see Sonic-style anthro’ ponies that are still ponies, and not just generic cat/hedgehog-style ones, like we’ve been seeing. (Nothing against those though. People can draw them however they prefer.)