Hi Dave,
I'm glad you aren't blocked anymore. Scheduling your own task seems reasonable enough for now. In VCD we'll continue scheduling customize-guest.exe instead of the script itself in order to delete the task until we find a better way to do it. This will make sure your task doesn't get scheduled twice.
It's a pain, so I won't let it go. But I don't have a better solution right now either. I can't see anything obviously wrong with the process management code. Anyway, it's already on my todo list and I've got some good ideas from this discussion. So, hopefully I get it fixed at some point.
Thanks for your patience. I know customization has always been a pain. But we have to support so many OS flavors and apply workarounds for sysprep and other weird stuff. If you get to the point you need features we don't provide, there are ways to extend it. It's not a rocket science. Just post a question and I'll provide guidance.
/Andrii