Creating a mesh out of a hierarchy

I'm parsing a B3D file by 'walking' through every child object. What I want to do is "cut" one child out of that hierarchy, and create a new mesh from it.
I don't want to use CopyEntity, I want a new, flattened mesh. How can I do this?

E.g:

B3D:

myEntity
....subEntity1
....subEntity2
....subEntity3
......bone1
......bone2
....light1
....light2

...and then grab 'subEntity1' and place it into a new mesh using something like createMesh()

Thank you