It would be unfair/unbalanced. Think of Itachi without the disease/health debuff.
At the end of the day, Sanji is meant to be equal to Zoro all in all, and Sanji has a lot of things that Zoro doesn't.
So to balance them, Sanji must "get/have" less than Zoro in combat, especially since Zoro is 100% combatant and Sanji is half a cook.
[automerge]1748293971[/automerge]
Sanji's his own person with his own fighting style, so if not CoC, he'll get something comparable.
If only the fandom is as wise as you...
There's many path to Rome, and there are different methods to make someone stronger, it doesn't have to be CoC/ACoC.
Like, it is possible & not unthinkable that the Germa serum is actually a Devil Fruit infusion, kinda like mini Green Blood.