So this decision for the super forms has always puzzled me, but I wanted to share my opinions on it and I think that super states being restricted to certain characters make sense. When everybody has something it's no longer special however, some characters should have access to the super state through the emeralds
Knuckles is literally the guardian of the master emerald which has the ability to empower and depower the emeralds, he literally had one in the past, and help deepen the lore anyway, and since Blaze is able to get around the Super rule due to being a guardian. Knuckles should too.
Amy is literally a hedgehog restricting the super form to gender is rather weird to begin with, Especially since a-lot of the fanart of super amy is really dope. That and Amy having psychic like powers would make a super form more interesting for her
Metal Sonic, and by extension every form of Metal Sonic, they're made to be robotic copies of Sonic, Eggman tends to get data of Sonic to make a metal duplicate of him, Plus both Metal and Mecha have been able to obtain a super state (although not a perfect one). So basically if they have Sonic data, or any form male hedgehog data they should be able to access a super state
Surge also applies to this even more, since she canonically have Sonic's bio data. So it's only a matter of time for her.
These are the only characters who should be able to achieve the forms naturally
The Exceptions
As you notice I didn't include Tails, in the ones who can achieve a Super Form naturally. While him having a super form does matter (Go watch the GameApologist video on that) I have a work around that and it through sharing energy. Tails should get a super from through Sonic and or other supers sharing chaos energy. This rule for Tails should apply for the rest of Sonic's friends. After that they should be able to achieve the form the natural way.
