A Java Application project provides a generated build-impl.xml which contains several -pre and -post targets which can be overridden to provide custom functionality (as described by the comment in the generated build.xml). However, such targets are not provided for a NetBeans Platform Application, so customisation is more difficult. Please provide equivalent targets in the ant files for NetBeans Platform Application projects.
Context: the page at http://wiki.netbeans.org/FaqIvy describes how to manually set up Ivy for a Java project. Step 4 uses targets "-pre-compile", "-pre-compile-single", "-post-clean". For a NetBeans Platform Application project, there are no equivalent targets. The "-javac-init" target can be used for "-pre-compile", but there appears to be no equivalent for "-post-clean".
OK, to get started, replay the Ivy FAQ for a NetBeans project, introduce "-pre-compile", "-pre-compile-single", "-post-clean" when needed and sent me the diff of your changes.
I can generalize that then. Reopen when you have the patch.
Btw. NetBeans supports http://wiki.netbeans.org/AutoUpdateTask, which is the official way to download (NetBeans) binaries.