[Mikatakujira Kunikunosaku]

More for my personal knowledge and teaching any readers, I will first quote the ability before my question.

Discovered by Mikatakujira Motonobu and used by the current Clan Head and his/her apprentice. Jiongu is not just one singular technique, but a separate living organism from the user. Much like a parasite, the roots that make up the mass of Jiongu will burrow into the host, consuming all the organs, muscles, and bones of the user but the teeth, eyes, and heart. As the roots consume the host’s brain they absorb all the knowledge and thoughts of the host, merging their own will with the will of the host. Becoming one entity the roots will try to entice and tempt the user to collect hearts from other of its kind, like a constant gnawing hunger, they will scream at their host body to take their sustenance from their peers. Though the roots can only support six hearts at a time, the gnawing hunger in the user’s mind finally quieting once they have reached this limit.

In turn the user can control the tentacle or thread like roots however they wish. The tentacles prove to be rather versatile, acting much like threads they can be used to sew up wounds stretch, or harden for attack, as well as being rather flexible and dexterous. After having the roots inhabit someone, they will find that as long as they keep a heart attached to at least some of the roots making up their body at all times, the user is functionally immortal, only dying once their threads are completely removed from any living hearts.

The part I am focusing on is "Much like a parasite, the roots that make up the mass of Jiongu will burrow into the host, consuming all the organs, muscles, and bones of the user but the teeth, eyes, and heart. As the roots consume the host’s brain they absorb all the knowledge and thoughts of the host, merging their own will with the will of the host. (...) In turn the user can control the tentacle or thread like roots however they wish."

So, my question pertains to the user's body. If the new body is just (a majority) roots, is it plausible a user can up and change FCs by 'willing' the threads to make a new 'permanent' body? IE a very drastic change, examples [skin tone, bone structure, body structure, even change gender mtf/ftm, combination or all]? (Restricted by level 2 appeal of course.) In the same vein, is it fair to ask if they can essentially use a semi-realistic henge w/o casting the jutsu if they can manipulate their body to such a level?
(Side note, the teeth and eyes cannot change <not without Jutsu and a lot of chakra iirc>, they remain the same through the entire process, that is a hard limit.)

My OC just has the threads forming vocal cords change so it is easier to identify which of her personality is talking and I feel that's pushing it. Appearance, body, vocal, VFX wise, what can it do and what's too much in this department?