The 'biggest' fanfic here is you claimed that Ashura have the chakra of Juubi or can produce Juubi chakra when only Gedo/Juubi can produce Juubi chakra. Hagoromo's chakra is not Juubi chakra but Hagoromo's chakra but have the same specialty as Juubi chakra.
Remind me again why only Uzumaki were chosen to host Kurama ?
-It bcus they have the most suitable body to hold that massive chakra.
Remind me why Naruto was not able to combine the chakra of the 9 bijuu with NE until gaining Hagoromo's chakra ?
-Bcus he is not Six Path power user on the level of Hagoromo nor he is a Gedo Mazo. He is just Uzumaki Naruto and not an Otsutsuki from Kaguya's bloodline.
Remind me why Madara amd Obito needed Hashirama cells to be JuubiJin ?
-It never been stated in Manga and Databook that you need Hashi's cells as a requirement to host a Juubi. So you want me to answer a fanfiction question?
Remind me how Ashura was able to use RSM without being a jinchuuriki ?
-Where in the manga/Databook stated that Ashura have RSM? That's the question I'm asking you first before we go any further. I want fact and not logical assumption even-though it could be logical but it just 'logical' but not means its a fact.
Mere words that people can interpret it the way they want will not help your case here bcus every words Kishi used to explain something in the manga came with less detail, in other words too vague. Especially anything related to Otustuki's back story.