If you loved One Piece: Adventure of Nebulandia, try One Piece: Giant Mecha Soldier of Karakuri Castle
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
You already loved

One Piece: Adventure of Nebulandia
→
Try this next

One Piece: Giant Mecha Soldier of Karakuri Castle
What they share
Both films are directed by Konosuke Uda, and they both carry the playful mood tag, and they sit in Action / Adventure / Animation / Comedy / Fantasy territory. If that's the register that drew you to One Piece: Adventure of Nebulandia, the second film will land in a comparable space — through a different lens.
playful
What One Piece: Giant Mecha Soldier of Karakuri Castle is
It seems treasure hunts are a pirate's life. The Straw Hats search for the Golden Crown on Mecha Island. Now they must stop Ratchet and a giant turtle from destroying a nearby island.