Consider syntax for using block at the beginning of a file:
It is convenient to have using aliases as a collection on CompilationUnit level, like "file.UsingAliasDirectives".
There are many places like this in ReSharper PSI, where accessors are published at a level higher than immediate parent. Here "alias" keyword is much more suitable.
If any syntax in path is a list, the type of alias is a list and collect specified items on all paths.