controller/index/arg ==> controller/arg?

[eluser]err403_love[/eluser]
Is there any way (without routing every URL) to allow CI to default to "controller/argument" if the index() function contains arguments? I don't want to have to set this for every controller in the routes (if you can even change this in routes, that is) and I would find this very useful.

Having to use a URL like controller/index/parameter just doesn't make sense.

I'm not sure if this is really possible though. If I configured it through routes, it would also try to reroute subdirectories, and I can't have that. I just really wish the URL would be "smart" and figure out that if that URI segment is NOT another function in your controller, and it is NOT a subdirectory, to treat it as an argument of the index() function, if it requires arguments, of course.

Thanks.