Creating NetRestore on 10.10.1 failing
'Customize Package Selection' is only valid for NetInstall images and not for NetRestore images - at least for Mavericks.  

Source

Probably it's the same for Yosemite. I haven't a source for that though.

On the other hand 'NetRestore' just uses an already prepared image of a working OS X installation - so absolutely nothing to customize afterwards...