Sandbar: Fluttershy (considering his cutie mark he seems to be good with animals and he is very calm)  
Smolder: Rainbow Dash (competition)  
Silverstream: Pinkie Pie (obvious)  
Gallus: Applejack (even if he’s sarcastic, he speaks up the truth)  
Ocellus: Twilight (both are well-read)  
Yona: Rariety (Rariety makes her new hairstyle…?)
 
Well we’ve to see what’s coming up the next episodes. They need more screentime to be more specific. And I don’t think that they “replace” the Elements of Harmony, but are the favourite students of their counterpart. IMO. No offense.

@Vaidelot  
Just you wait for G5

@Joshua  
No, actually I think Yona actually works best as Rarity, Smolder as AJ, and Gallus as Rainbow Dash.
 
Yona’s introduction has her excited about sharing yak culture and she also has some fashion consciousness with her braids.
 
Smoulder shows to be ultimately honest about everything - even if it insulted Yona’s heritage and she pulls no punches on how she thinks about others.
 
Gallus is trickier - he doesn’t get much chance to show off loyalty EXCEPT when he saved Sandbar from Yona and is the first one to speak up about staying at the school.

@Vaidelot  
He’s one of the friendliest of the lot, though.

I think there could be a bit of a problem with this one…

@Dustcan  
Spike

@Background Pony #BD83  
Nah, she’s Applejack’s inspiration.

@Joshua  
maybe yona?

Okay but who’s the Starlight of the group?

@Background Pony #BD83  
Maybe, but I don’t know if Smolder shares the same qualities as Rarity.

minor problem: gallus was more interested and inspired by dash.

Seems legit