Don't the Mane Six care how their Rainbow Powers ruin their looks?

[Princess Lona 382]

couldn't they write a new episode that deals with the Mane Six's perceptions of one another when they transform? Aren't they conscious enough about their looks that they'd want to let Rarity help change them?

Since the aim of the show is to teach young children about friendship, to encourage them to focus on things that are really important as they grow, and to foster positive self-image, I don't think they would devote an episode to having the Mane Six get all self-conscious about their looks. The Mane Six are good friends and they don't care what the others look like. Even Rarity knows that it doesn't really matter what a pony looks like or what style they choose. When she gives another character a makeover, her focus is on bringing out the best in them, using fashion and style to accentuate what is already beautiful about their personality. Plus, despite what we may think, the Mane Six all seem to like the look of the Rainbow Power. If they could hear the way people responded to it, they would probably shrug and say "Haters gonna hate".