Fleeing the Wandenreich for One Piece

The answer for the Bleach version has already been revealed: crossbreed bloodlines, obtain the Gluttony-Gluttony Fruit, then go back to the Bleach world to capture a Shinigami and a Hollow, directly synthesizing them into a mini-Soul King. This way, you get both stats and mechanics, and you can also enjoy the same treatment as Ichigo Kurosaki—a three-year speedrun, buddy!

The Grim Reaper isn't someone who can easily defeat pirates; no matter how much he gets stronger, he can't possibly beat Yhwach.

A rare author whose writing gets worse with each passing year.

Is this a level four author? The premise is so brainless! After being transported from Bleach to One Piece, due to some rule, spiritual power becomes Haki, and then it turns into chakra in Naruto! I haven't seen such a ridiculous premise in ages.

This dual-travel mode makes it easy for the early-game power stacking to collapse, and it's also difficult to write other NPC characters in the mid-game. I feel like this book will be a complete flop.

That's a bit much. The Wandenreich's high-end combat power is unmatched by pirates. Also, the Quincy actually specialize in killing souls, and Shinigami are essentially soul beings.

The power levels are completely messed up. Shinigami (death gods) all attack souls, so immortality might not be effective. Besides, how could Whitebeard possibly be a match for Yamamoto? One slash and he'd be dead.

The most powerful abilities in Bleach are all rule-based or mechanic-based, or hybrids that manipulate stats. And then you go to One Piece and eat a Dragon Fruit? Mythical Zoan types are just for fun; the truly powerful ones are Paramecia types. And One Piece has Haki.

The protagonist ate a Mythical Zoan, and several members of the Sternritter noticed something was amiss. If he were to compete for the Sternritter position, Yhwach would surely notice as well. In a situation like this, being suspected would easily make him a traitor.

I thought I could write something different about Quincy spiritual power compared to One Piece, but it turns out to be just another One Piece story in Quincy skin. It's truly a dissertation defense.