Since in the newer versions of Audition all configuration files. presets and favorites are stored as .xml files I would think it would be sensible to extend those to be editable and scriptable.
But a fully supported SDK would also be useful for those with more low level programming skills.
I would obviously vote for Windows Scripting Host, since it gives you access to the .NET CLR, but there's the small caveat of OS lock-in...
Either way, the ability to do disk operations, write your own GUI, even include network access and third-party API:s like Perforce has proven a godsend when scripting for Vegas. Whenever Vegas doesn't supply me with the tools I need, I can very often write them myself.
Python scripting gets my vote!