I don’t believe there has been such a userscript yet… however, there are some WK-ified Anki decks floating around, most notably the awesome ones by @hinekidori that have been modified by @eninny. They emulate WK because you can input your answers.
https://community.wanikani.com/t/genki-anki-wanikani-template-ver-26/11638
As an example.
Also when you’ve reached max level, there is an excellent script by @rfindley, the “Self-Study Quiz”.