The problem with your route is that by using :any you match, actually...ANY route, so you're pretty much stuck there.
I think you might have two solutions:
1)You can selectively re-route all your sites controller individually, like:
$route['aboutus'] = "aboutus";
$route['where-we-are'] = "whereweare";
//And do this for all your site's controllers
//Finally:
$route['(:any)'] = "polica/ogled/$1";
All these routes must come BEFORE the ANY, since they are read in the order they are presented, and if you place the :any at the beginning it will happily skip all the rest.
EDIT after comment:
What I mean is, if you're going to match against ANY segment, this means that you cannot use any controller at all (which is, by default, the first URI segment), since the router will always re-route you using your defined law.
In order to allow CI to execute other controllers (whatever they are, I just used some common web pages, but can be literally everything), you need to allow them by excluding them from the re-routing. And you can achieve this by placing them before your ANY rule, so that everytime CI passed through your routing rules it parses first the one you "escaped", and ONLY if they don't match anything it found on the URL, it passes on to the :ANY rule.
I know that this is a code verbosity nonetheless, but they'll surely be less than 6K as you said.
Since I don't know the actual structure of your URLs and of your web application, it's the only solution that comes to my mind. If you provide further information, such as how are shaped the regular urls of your app, then I can update my answer
/end edit
This is not much a pratical solution, because it will require a lot of code, but if you want a design like that it's the only way that comes to my mind.
Also, consider you can use regexes as the $route index, but I don't think it can work here, as your usernames are unlikely matchable in this fashion, but I just wanted to point out the possibility.
OR
2) You can change your design pattern slightly, and assign another route to usernames, something along the line of
$route['user/(:any)'] = "polica/ogled/$1";
This will generate quite pretty (and semantic) URLs nonetheless, and will avoid all the hassle of escaping the other routes.