Here is the round two version of my scale, with some feedback from Checkmate and the others. I think it's also possible if multiple characters are changing in your story you could list out each of their change intensities individually. This might be useful if you have only 2-4 characters undergoing changes. As an example of this, if your story has three women walking in the park and they are transformed by a random avatar into a man, bimbo, and their dog, the numbers would be Phys/Ment: 2/3, 1/4,and 5/5. In the grand scheme of things it might not matter, but maybe people won't be as put off is there is only one large change.
Transformation Change Scale
Physical
1. No change or only superficial changes: change within human norm (ex. skin or hair color change) (<10% changed)
2. Minor change: extra-human change, but still recognizably human (ex. extra arms, limbs, possibly even gender shift) (10-30% changed)
3. Moderate Change: significant change to the baseline, but still recognizably human (30-50% changed)
4. Severe Change: Extreme deviation from the human norm (50-75% changed)
5. Massive Change: unrecognizable human (>75% changed)
Examples using common belial transformees.
1. "cock"-tails from Tales of Jizza2: allows woman to grow a cock
2. Sutonian woman: minor changes to feet, growth of a tail and male appearing genitals, but the form and function of most of the body stays the same.
3. Britney from Belial idol: armless pain slut humantaur, but changes are still built around baseline human.
4. Freyan cockwoman: Massive changes to upper torso and growth of balls, but lower torso is mostly unchanged.
5. Sutonian whore: composed of human parts, but barely human looking. Body reduced in size and function
Mental
1. No change
2. Minor change: weak compulsions or light changes in thinking
3. Moderate Change: strong compulsions or change in mental processes
4. Severe Change: Massive mental change, barely any of the original subject remains (ex. sex beast or pet)
5. Massive Change: Total loss of identity/mental function
Examples using a transgender transformation (MtF).
1. new woman is now a lesbian, has many male habits and mannerisms
2. new woman is bi or gender confused, has gained some feminine mannerisms
3. new woman is straight and able to pass fully as her new gender
4. new woman is nymphomaniac and hyper feminine.
5. new woman possesses an entirely new personality, doesn't think of herself as her pre-transformed form.