Why is it useful?
For badly-behaved apps that require additional configuration or cleanup, it is useful to have pre and post uninstall script functionality available. This is already available in PMPC Cloud for all app types, but in PMPC Publisher, it is not available for EXE-based uninstallers built with PMPC Custom Apps. This, in turn, means that it is not available in Configuration Manager. This is documented here: Uninstall a Custom App > Limitations.
Who would benefit from it?
Customers that use PMPC Custom Apps for apps not in the PMPC catalog and that use Configuration Manager.
How should it work?
In Publisher, implement the Uninstall tab for PMPC Custom Apps that use an EXE (un)installer that works the same way as the Uninstall tab for all other app types.