A great news from r4i-sdhc team:
R4i team will release a new updater soon that can flash B9S to NDS flashcart or reversely, more details: click here. [2017-9-29]
Currently r4i-sdhc is still working on it, and the download link for B9S updater will be made available within a few days.
Following are a few pictures released by them: