Thanks for the feedback. All the use cases you list are good info. What is your opinion on what advantage there is to having the calls be made via the build spec as opposed to writing a VI where you make the calls before and after BuildTargetBuildSpecification?
I forgot to ask you to elaborate on this point:
Some way to programmatically access build parameters and pass data between the build-hooks (and pass errors out of the build steps, in order to abort the build)