A very interesting thread i must say.
I have two questions regarding this suggestion by japhy:
$obj->ChildClass2::method(...);

1. What would the (implicit) first parameter to the above call be, the class name ChildClass2 or the object $obj?

2. If the class name is being passed then thats no big deal because we could rather do this instead : ChildClass2::method(...);
If $obj is being passed as the first parameter to the subroutine call then i don't see much use of a concept such as inheritence at all as any method from other classes can be called like this: $obj->ChildClass2::method(...); as long as you have an object to some class.

Thanks in advance for all your answers.