I still think when it comes to characters intended as idealised audience surrogates, they’d have a higher chance of being Canon Sues than even those based on their authors if because it’s not uncommon for writers to base characters, stories and poetry from their own personal experiences and sentiments. It’s like if Barry Allen were to substitute for Dante Alighieri and if Caitlin goes wolf, it would be a modernised Divine Comedy really.
Likewise if Black Canary and Green Arrow were Tim’s biological relatives, there wouldn’t be any need for Dana Winters but they’d all act more like Elvira, Scoorge and Donald. No seriously, that could really happen. As for Kitty Pryde, what makes her Mary Sue’s that writers tend to hold her back from what she’d logically or organically become.
That too isn’t unique to other characters but they’re not intended as idealised reader surrogates to begin with. Though that necessitates a direction where Kitty wouldn’t just stick to being an assassin like she is in Age of Apocalypse but also become the character Psylocke ended up as. But because Psylocke wasn’t meant to be a ninja and she even yearned to return to her old self until recently.
Especially due to the body swap whilst Kitty Pryde would easily become that character without the body swap. That’s still saying in the sense of characterisation that it seems writers seem afraid that Kitty would easily be how Psylocke was mostly represented as. Even if she actually got ninja training first.
But again that necessitates having to free all three from being reader surrogates that this would be the only path against Suedom really.