My interpretation of the linked blog post is that you would export from C2 for Cordova? the same as if you were going to build with XDK or Cocoon.
Then in the new build service I guess you will import the project.
I could be wrong but I don't think you will need the plugins to be ported to C3 in this case because you're not opening the project in C3 to edit it.
Is that right Ashley ?