You can get most of the way to functions outside of a class with "using static". I often do "using static System.Math;" to have bare may functions. Also often do the same with System.Console.

I'm not sure what your thoughts are on Structural Typing, but I've found liberal use of extension methods on interfaces to be a really useful way to get lots of functionality on a wide variety of types.

As for your comment on namespaces, I cannot agree. Again extension methods would not be anywhere near as useful if one can't arbitrarily add code to any namespace, without needing to adhere to a file system structure.