I hope I am understanding this correctly. Can you add the SW style instruments and then before you rebuild, freeze the EV style you wish to keep?
I think I accomplished a similar problem yesterday when I created a new song by copying a rubato EV 32 bars into a second swing file, but freezing the swing file before pasting. Then going to the "Edit Settings.." and muting and un-muting the various instruments.

Last edited by jazzsax; 09/01/15 08:54 AM.