I don't think that's how it works. Remember, one of the rakshasha said that they are basically human turned to demon. But 'humans' with the ability of a rakrasha by killing or eating them are still considered humans. The only difference is that, humans have rakshasha's blood flowing in them, while the rakrasha's are basically borned and made demons.
But if that blood flowing in human got into the hands of gluttony rakkshasha, then there is a possibility that it will copy that power
Hmmm, for me I don't think so. He can only absorb and eat from a rakshasha specifically. And Han Maru as a gluttony rakshasha ability user, only feel hunger towards them. As we all know, he is kinda different form the other user. And rakshasha ability users, can only activate their powers when there's a yellow dust. Han Maru can create his own yellow dust and has a better regenerative ability, with that he don't really need to absorb from the other users, he specifically said that the more he ate other rakshasha, the more he become stronger. Thus, this implies that he's target are rakshasha only.
Also, based on the recent chapters, I don't think he can't absorb abilities from the other users. He can only absorb from rakshasha so thats where my opinion comes from (๑•ㅂ•)و✧
Wait... So if people with Rakshasha's power are basically just rakkshasha, doesn't it mean that Han Maru can eat other people, and gain their power... So.....