2-natural transformation?
(Power) Any bicategory with finite bilimits is equivalent to a strict 2-category with finite flexible limits.
Let $K$ be a bicategory with finite bilimits, let $K \hookrightarrow [K^{op},Cat]$ be its Yoneda embedding, and let $K'$ be the closure of $K$ in $[K^{op},Cat]$ under finite flexible limits. Since $Cat$ is a strict 2-category with finite flexible limits, so is $[K^{op},Cat]$. And since $K$ has finite bilimits, and these are preserved by its Yoneda embedding, while flexible limits are in particular bilimits, every object of $K'$ is equivalent to an object of $K$. Thus, $K\simeq K'$.