For example... I want to try something different for the traditional hengeyokai, using a shared racial trait rather than the clumsy and never really fitting methodology of just making them "one race with animal form as window dressing difference". Which means I gotta start with that one shred racial trait...
Hengeyokai: You belong to a race of magical beasts that can assume partially or wholly humanoid form, as well as revert to your true bestial shape when it suits you. As an action, you can shift into any one of your three forms.
Hybrid Form is your default form. It functions as normal for a character.
In your Human Form, you gain Advantage on all Charisma (Deception) checks made to pass yourself off as human. It otherwise functions as Hybrid Form.
In your Beast Form, which is determined by your race, your game statistics are replaced by the statistics of the beast, but retaining your alignment, personality, Intelligence, Wisdom and Charisma scores. You also retain all of your skill and saving throw proficiencies, in addition to gaining those of the beast; if you and the beast have the same proficiency and the beast’s bonus is higher than yours, you use the beast’s bonus.
Changing shapes does not alter your current hit points, maximum hit points, or hit dice.
You can remain in any of these three forms as long as you wish, but must consciously choose to change shapes.
You can change shapes once at 1st level, twice at 5th level, and thrice at 11th level. You regain all expended uses of this trait when you complete a long rest.
If you have exhausted your uses of shapeshifting, you can revert back to hybrid form, but you cannot then change again into beast or human form.