Is it possible to change the requested component and view with a system plugin?

Question

For reasons beyond the scope of the question, I want to be able to effectively (but not actually do a redirect based on various parameters.

If the request IS index.php?option=com_something&view=default

I want Joomla to display index.php?option=com_alternate&view=override as if (in every respect) that was the original request to begin with.

Can a system plugin accomplish this? And if so, on which event?

EDIT For clarity of requirement, this sample pseudo-ish code programmatically demonstrates what I'm envisioning. Before spending hours or days, I'm "checking the premises" of my intended approach.

// Effective Redirect to com_content (as an example component) without classic redirecting
class plgSystemMySystemPlugin extends JPlugin
{
    public function on[Before|After][SOME-SYSTEM-EVENT]() {
        jimport('joomla.application.component.view');
        $options = array(
            'name' => 'article',
            'base_path' => JPATH_SITE.'/components/com_content'
        );
        $view = new JView($options);
        $view->addTemplatePath(JPATH_THEMES . '/' . JFactory::getApplication()->getTemplate() . '/html/com_content/' . $view->getName());
        // Set Item, Itemid, etc. somehow here
        $view->display();
        JFactory::getApplication()->close();
    }
}  

Answer 1

The currently accepted solution is overcomplicated and bound to cause problems. Don't mess with fundamentals, like the URL and PHP superglobals when all you want to do is modify Joomla's routing results. That's what the onAfterRoute event is for.

Create a system plugin. Create a public function onAfterRoute. In there, get $input = JFactory::getApplication()->input. It is populated with the parsed request. If option and view and whatnot matches your criteria you can change it with $input->set('option', 'com_alternate') etc.

This solution also works with SEF URLs since it runs after Joomla has parsed the SEF URL. It does not mess with the displayed URL. It only changes how Joomla understands the URL, i.e. the routing.