Has anyone satisfied the UK fiancee/spouse visa financial requirements by working their foreign job remotely as someone self-employed in the UK?

I’m a UK citizen with a Japanese fiancee. We plan to get married in the UK, so we want to apply for his entry under the fiancee visa. However, we don’t meet the financial requirements yet — I’m searching for, but haven’t yet secured, a UK-based job. That said, I have a Japanese job that meets the income requirement and would be willing for me to work remotely.

I spoke to a Japanese visa firm who suggested it would be possible to count J-income if

  1. I paid tax on the income in the UK.
  2. I became self-employed in the UK and submitted that documentation.

However, it seems like the forms for the self-employed look to a past year of s.e. income, which I don’t have.

Tldr; Has anyone satisfied the UK fiancee/spouse visa financial requirements by working their foreign job remotely as someone self-employed in the UK?