ActionView#assigns lost its usefulness

In Rails 2.3.4 I was able to do something in the lines of:

@view = ActionView::Base.new
# later:
@view.assigns[:foo] = 'bar'
# finally:
@view.render(:inline => @template, :locals => locals)

That is, update the assigns list after instantiation and have it affect the rendering.

In Rails 3, the assigns hash is copied to local instance variables immediately in the initializer. This hash is copied to @assigns and exposed through an #assigns accessor like before, but this object is never used internally again and thus writing to it has no effect. The only way to pass assigns now is during the initialization:

@view = ActionView::Base.new([], @assigns)

This seems like a regression because the old way was certainly useful.