Making Shiki a canon character solves the same problem as did tying Ochoku to Beehive: it allows Oda to explain where all these powerful characters went without having to waste too many panels.
shiki IS canon already...
We literally saw him in god valley, chapter 0, higurashi etc etc
But Strong World cannot be canon. It doesn't fit into the time line. And fresh out of post time skip goofy beating a prominent Rocks pirate is egregious and insane.
It's a worldbuilding shortcut.
Making this character shiki is the exact opposite of that lol.
That means Strong World is either canon, which i already explained is problematic.
Or Strong World never happened. Which is even more insane. As that just completely erases the significance of the movie and the work people put in it. Shueisha ain't about to allow that.
The best way for this to resolve is to make the character someone else entirely. That way, Shiki can be still canon, and Strong World can still enjoy it's pseudo-canon status.
Also, making this character shiki is just shrinking the world of op. There's plenty of characters oda could make it, or even more characters he could create from scratch. But going back to a character that was already defeated in a movie is just lazy as fuck. And raises a lot of issues in the already disastrous canon timeline of op.