Extremely cursed idea: The Hepburn romanization for Japanese doesn't use up all the letters in the Latin alphabet, so we can borrow an idea from Nihon/Kunrei-shiki, "one kana, two letters", and the c, q, x from Mandarin Pīnyīn and replace Hepburn's ts -> c, ch -> q, sh -> x. Now I know all the linguists out there are screaming since the first two are aspirated Pīnyīn letters representing unaspirated sounds in Japanese, but it's fun to put those unused letters to use and make everyone angry!