Keep in mind that I don't want to use the GAC since my assemblies are frequently updated and I do not wish to register them after each update.
You could probably use NTFS directory junctions. I haven't tested but they should work.
I am of the opinion that since the framework version isn't mentioned, further clarification is needed about the purpose of specifying a common BIN folder. Do you intend to have a common output directory or do you want to load compiled assemblies from a common directory?
I believe the codebase
element would be appropriate in this scenario, because the probing
element can only specify subdirectories of the application.
Take a look at this MSDN article
This raises flags about bad deployment and source control practices. Are these libraries that are shared between multiple applications? Are you sure these libs should all be updated independent of their respective applications?