I can tell you about the race thing which is it has a very high chance for this answer, which I apologize is prolly not. the main character wouldn't really work with any other races due to the entire plotline requiring them to be human for a lot of the dialog to work, like if you were a Lizardfolk the people of Bareshade would have a lot more issues with you and you wouldn't be able to bond as fast as a human and the Lizardfolk would just trust you as one of them which kinda changes a lot of the dynamic's of characters requiring it to change how they are written, it also removes any player incentive to introduce them to humans since they aren't one and wouldn't gain anything out of it.
or if the MC was an Orc, then Northcrest just straight up wouldn't be something you could do as they would chase you away or arrest/kill you as soon as your seen.
Werewolf would cause Logan's, Bernard's and Caleb's entire storylines to change as well, Caleb's due to him being with the wolves and he may be wary as you did nothing before now and Bernard's because you were always one and his best friend was taken by them so he may think you had a part in it. Then Logan's is due to his intense hatred of all wolves, which if he found out you were one after you told him of his wife's infidelity, he might think you were involved and hiding it and he would suddenly hate MC and maybe he would try and fight us/kill us.
if we were whatever the fuck the Nameless is I don't think the teacher would have ever taken us in and maybe we would need a whole ass new dimension to start in lmao.
Minotaur just similar issues to the Lizardfolk thing except lizards also wouldn't trust you since you're not a lizard.
actually, as I'm typing this there is a solution to the issue, not the best one but you start somewhere else and what your goal is could change too, would take a SHIT TON of coding and content to be added as it would pretty much use none of the previous content and would need some minor changes to interactions and new interactions too...
like maybe Bear, Red Panda, Boar, whatever the innkeeper in Tao's home is again would all start at Tao's hometown and the goal is to save Tao but along the way you find a dead herbalist and they wrote down a note stating they are seeking their teacher and you can take over.
Lizardfolk excluded from the thing above as they would start in the tribe and the goal would be stop the nameless and he would never get a gem due to him being unable to reach this MC as he is protected by the barrier. then they would eventually end up in the same spot as the other one meeting the human herbalist who is dead with a note stating his journey and this MC wants to continue their wish for some reason.
Orc's maybe you would need to choose which Tribe you're from? and depending on the answer you could have support from your people or be against everyone in your tribe and seeking the other tribes for help against whatever is changing you people.
Werewolves.... I don't think this would be possible as MC would either have to found out Antilycan existed a LONG ass time ago or was always one and somehow never lost his mind? maybe the teacher took them in to study Lycanthropy and went away for more materials and since MC doesn't have anyone else they want to find the Teacher as they want to become human again? even then kinda a Strech as maybe the teacher would chain a werewolf if it was his test subject.......
Ratkin you could start at the scrapyard and befriend scrap sooner or maybe have been friends for longer? like you've known each other a while but you were smart enough to leave and study other shit and your goal is to either overthrow the Rat king or take scrap away and give him a better life with human's?
Incubus/Succubus would maybe only be able to travel at night and would start in Viccoria's cave with a shit ton of sex experience and friendly relationship with Viccoria and you could bring in more victims or try and become more human like and befriend people.
swamp creatures just are mindless drones of big tree so either you gain sentience, or you don't get this as an option. also, you couldn't talk to people so like, I don't think it would work.
I don't know how a minotaur story would start. maybe Northcrest or just some far ass place in the future.
same with the Cthulhu thing nameless is, I only got weird pocket dimension for an idea but feels like that wouldn't work well.
all the issues from the first bit would still be present but the starting issue would change as you have different places...
along with the fact even adding ONE extra race would prolly take an entire month or maybe even 2 just to start due to how many things would need to be changed, so like Hyao most likely will not be doing this due to the sheer amount of work it would take and how long it would take, if he worked on it in the background and make a shit ton of smaller updates and eventually added it in as one major update after maybe a year of it being on the sidelines while he had smaller updates but I don't know if Hyao would want to do that lol.
oh, also Hyao had a poll like 3 years ago where he asked if we wanted a drawn MC or a blank one so we could get more scenes as they would only be written compared to needing a new CG every time if MC was drawn. if you can't guess we voted blank so we could get more scenes lmao. so maybe that could influence his choice of more Races or not.