+1 but include the possibility to add a new generic parameter with default value similar of adding a new parameter to a method with default value (see http://devnet.jetbrains.net/thread/303411? )

class Foo<T> { }
class FooDerived : Foo<T>
//"Change signature on Foot<T>: Add parameter and update usages with default value of "int"
class Foo<T, T2> {}
class FooDerived : Foo<T, int>