It is possible, but not practical.
Sprites already have a significant impact on project performance, and adding this feature to a delicate object such as 9-patches would make the situation even worse.
You could use Sprites that simulate 9-patches. Of course, they are not the same thing, but it is better than adding a feature that not everyone would expect to have.
You may also want to see this post made on the Construct 2 forum.
Triggered when a layout is run for the second time