Route to e.g. MyController, if controller from URI not found

[eluser]Unknown[/eluser]
looks like this is the best option:

Code:

$route['404_override'] = 'legacy';

EDIT: actually, doesn't look like this'll allow me to keep the URI segments... if this is a viable option, is there a way to pass the original URI (or segments) to the 404_override?

EDIT: data still exists in $_SERVER['REQUEST_URI'] - i think this is solved (although feels a bit hacky)