I saw the MLP G5 concept art leaks and… Boy, are they bad. So I decided to make my own.
 
Twilight Sparkle  
Okay… So… Who was the idiot that decided “Hey, wouldn’t it be great if Twilight, the pony who’s extremely magic oriented, was a pony that didn’t do magic?” Like what??? So, of course, I made her back into a Unicorn. I noticed how the tried to make each race more unique- and I like that! So I made it that Unicorns have those traditional unicorn tails, and have little cutie mark-shaped hooves. I made her hair violet and pink because Hasbro really doesn’t seem to like dark blue, plus it doesn’t look that bad, I based the hairstyle off of one of the designs that I liked. I also gave her a more “royal” muzzle since she is from Canterlot.  
As for personality, I think that since they don’t want the whole “magic is commonplace” deal going on, I think Twilight is going to be an aspiring magic-scientist. Like, she studies magic and wants to understand it and be better at it, but she’s not some magic master like in G4;
 
Applejack  
Hey Hasbro, here’s a question: Why???  
Anyway, She’s basically the same, but I added a bit more green, toughened up the muzzle and body structure a bit, and changed her hooves because I wanted Earth Ponies to have fluffier legs with more realistic hooves. Gave her the white markings since most of her designs had them and they looked cute, also gave ‘er a bow on her tail because it’s kinda cute.  
For her personality, I think she’d be more serious, blunt, stubborn and sarcastic. She’d still have a cowboy accent but it’d be more subtle;
 
Pinkie Pie  
Okay so, all the Pinkies were almost good but still bad. I decided to keep her as a pegasus since I’ve always liked that concept, but didn’t give her the weird poofy wings most of them gave her. I made her hair a bit poofier and more cartoony, and she has a more childish face and a chubbier body just in general.  
I really like the style of wings they gave her and Dash in one of them so I decided to go with that, I also thought it’d make sense for the Pegasi to have cloven hooves.  
She’d probably have mostly the same personality as canon, but she’d probably make a lot of visual flying jokes and sometimes get so excited she starts flying;
 
Fluttershy  
Since Pinkie’s a Pegasus I gotta even it out by making Fluttershy an Earth Pony, which to be honest kinda fits her.  
I gave her very soft colors, I changed her muzzle, eyes, and hairstyle to match her in the leaks, since she looked very nice. I also really liked the new Cutie Mark so I gave her that. She also has the realistic hooves and fluffy legs because Earth Pony. I gave her thin eyebrows because I thought she might need them for her “default” expression and for The Stare™.  
As for personality, I’d like to see her using though love more. Like, the whole thing with the Breezies and Tanks for the Memories;
 
Rarity  
Okay so, probably the first thing you noticed is I made Rarity blue, which isn’t something you normally see, but I have an explanation for that!  
I wanted each character to have their own representative color of the rainbow since Elements of Harmony and Rainbow Power and blah blah blah. Thing is, Rarity doesn’t have a main color. Her most noticeable color’s white, which isn’t even a real color, so after some experimenting, I decided it was best to have her color be blue, so I made her coat blue.  
Moving on from that, I gave her a longer muzzle because I thought it looked nice and fit her, I also made her body type a more… angular? I don’t know how else to explain it. The mane and tail ideas came from a few of the concepts too. The idea for the Cutie Mark came from her initial Rainbow Rocks design, oddly enough. I also gave her eyebrows because I thought she needed them since she’s the most dramatic one.  
For personality, I’d like to see her giving out free dresses sometimes because she just thinks that dress would fit perfectly with a specific pony;
 
Rainbow Dash  
Okay, so Rainbow’s pretty much just one of her concepts so I don’t have much to say. I like her with short, spiky, slicked back hair; It fits her being a Wonderbolt and such. She also has bigger wings with a rainbow tint, that way she really is a flying rainbow. I made her white with red eyes because I kind of like imagining rainbow hair as a kind of pony-albinism? And because it’s the sum of all colors light-wise.  
I don’t think she’d change too much personality wise.