I want to try and write a fanfic about Subaru getting reincarnated as rudeus, but I need some other opinions

So I want to try to write a fanfic in which Subaru instead of getting isekaid into Rezero he becomes rudeus in Mushoku tensei

There are just a few things I was debating over.

1. Would Subaru be able to use something like the flow method

2. Who would be his love interest
   Currently debating between either nanahoshi who might be a bit to young or Roxy which I am also iffy about

3. How should other characters call him(Subaru for convenience sake, rudeus for lore accuracy or something in between)

It would mean a lot to me if you could give me your opinions 🙏