I'm using the SBS Tankentai, but a have a question.
I would add another pose of attack for the skill...
You can change a little piece of code by adding another skill?

You have to study the whole tankentai system custom action mechanic. There's no other way.

There's a few tutorials for VX, check out Mr.Bubble signature for the links.
And i must warn you, it's not easy to do.