Hrhmhmhm i might try something.
I mean I tried Mario / One Piece and I tried Persona / Discworld, to varying degrees of success, so I'm used to stupid-sounding crossovering.
Vimes the Marine? Past shenanigans involving an Admiral Keel and the Time Time Fruit? Vimes would certainly have a strong opinion about which "Justice" to follow.
Chopper studying under "Granny" Kureha on becoming a witch-doctor could work as well.
I'm guessing the best way would be to just fuse both worlds, giving a focus to One Piece setting, and Disc characters. Magic and narrativium can be used to explain any xcuse for the plot.
Captain Vimes the "Smoker" (due to the cigars), "Granny" Kureha, Admiral Vetinari, who came out of nowhere and happens to think
unconfortably outside the box. Lord Rust could work for both Akainu (dangerous absolutist tendencies) or Spandam (innefective villain of the week). Toby "Carrot" took the world by surprise in single-handedly arresting Alvida even before becoming a Marine.
All the while the Wizards are the only ones who remember that the worlds used to be separate and are trying to fix it, forming the Archchancellor's Pirates ("
Avast! But why not the Dean's
pirates, yarr?" "
Upon my word Dean if you keep talking like that I'll use the plank in such a way that you'll wish you were walking on it.")
The other way around wouldn't work; One Piece characters in the Disc would be way too out of their element. It's not a setting that lends itself well for action shounen.
