Supporting an unsupported .NET library, possible?

Suppose I used a .NET class or method that is not supported by the Unity’s Mono Compatibility. That’s, the method or class from a .NET library that is not listed on http://docs.unity3d.com/Documentation/ScriptReference/MonoCompatibility.html.

I add a reference to the DLL of the .NET class that is not compatible with Mono in MonoDevelop so that the dependencies in my code are okay.

Now if I were to compile this way in Unity, would it work well? That’s, even if a class or method is not supported by Unity’s Mono, would adding a DLL reference to the unsupported .NET library make Unity supports it?

I asked this because adding references to the .NET dlls is almost the same as adding my own dlls. Unity works when I add my own dlls, but I don’t know would Unity compiles if I added a ton of .NET dlls.

I doubt.
if it was so easy to add compatibility to the other classes, Unity would make everything compatible, don’t you think?