Peach panties were present in Melee and Brawl, that doesn't turned her into the next "Samus" perverts will always be there, Palutena, Peach or any character could have been censored, that isn't stopping "fans" to release crazy amongs of naked or fetish pics or drawings on the internet.
Smash had 3 females before and only Peach panties were posibly visible, of all new females newcomer only Palutena has a skirt open to her uper leg, maybe this prevent her for getting the dark treatment Peach got now, because the censor would cause the character to look odd for some moves if somehow the censor becomes visible while fighting,(imagine fighting and seeing a black thing between her legs, far worse than her using panties) Peach doesn't have that problem her dress cover everything baring the feet and to see her panties you would need to make a move and pause the game in that specific situation and then rotate the camera, just like in the image above.
In my opinion it's not going to be harder to be a fan and I could care less about freak art, they will exist with or without panties, for me this is not a reason to complain women wear panties, I am sure this is not Sakurai deliverely leaving Palutena uncensored, I am sure this is to be with movement problems with a black shadow between her dress for the very same nature of it.
This is going to be a big deal if people do a big deal like with the "pole dancing taunt" people did a big deal and it really isn't that grave, yeah you can see Palutena's panties if you try, for me this means nothing, I play the game to enjoy it, if some perverts like to take pictures of her underwear well that doesn't take any from the character to me.
Don't get me wrong sexualization is a thing on videogames, but Smash and Nintendo girls are of the less sexualized out there, just look at mmmm almost every fighting game, unrealistic armor, unrealistic physics, unrealistic fighting clothes, over the top bodies far more suggestive languages among others. Even Zero Suit Samus I don't see any issue with her, some people claims she is getting sexualized, but the thing is she has always been sexy since Metroid I.
In my opinion there is nothing wrong with a little sexyness, women in real life can be sexy this don't take away anything from them, it is part of their femenity, Palutena's panties are far from being an issue I will complain when in Smash I see something like this:
Just no
About the ESRB if my memory is correct Smash is E+10 just like Uprising and we got this:
Even when Amazon Pandora's outfit is purposelly sexy, this is nothing like things we see in tons of games like Ivy Valentine above, you just have to put things into perspective, both people claiming for zero sexyness in characters because of sexualization and people keeping purchasing games with over the top females bodies in ridiculously thin outfits are BOTH wrong, Smash is no near to have any of those issues. The females in the game are just fine, likeable but nothing over the top.
I recomend you not to look to much into the issue you addressed, as I said before this is going to be a big deal if you make it a big deal.