Talking about the "single piece of software that makes all the features of the rig available", have you checked out Hamlib recently?
It's an open source library designed at controling rigs (and antenna rotators), offering an "hardware abstraction layer" to applications.
It's developed under Linux with builds on other systems. Currently, we're seeking GUI developers
and people to help the port to win32.
Site is at http://hamlib.org
73 de Stephane