The problem with your route is that using: any that you match is actually ... ANY route, so you pretty much got stuck there. I think you can have two solutions:
1) You can selectively redirect all the controllers of your sites individually, for example:
$route['aboutus'] = "aboutus"; $route['where-we-are'] = "whereweare"; //And do this for all your site controllers //Finally: $route['(:any)'] = "polica/ogled/$1";
All these routes should arrive BEFORE ANY, as they are read in the order in which they are presented, and if you put: any at the beginning, he will gladly skip everything else.
EDIT after comment:
I mean, if you are going to match any segment, this means that you cannot use any controller at all (which is the first segment of the URI by default), since the router will always redirect you using your own law. To allow CI to execute other controllers (no matter what they are, I just used some common web pages, but maybe literally everything), you need to enable them by excluding them from re-routing. And you can achieve this by putting them in front of ANY rule so that every time the CI goes through your routing rules, it first analyzes the one you "escaped" and ONLY if they do not match anything found in the URL address, it passes to the rule: ANY.
I know this is verbosity, though, but they will probably be less than 6K, as you said. Since I don't know the actual structure of your URLs and your web application, this is the only solution that comes to my mind. If you provide additional information, for example, how the regular URLs of your application are formed, then I can update my answer
/ end edit
This is not a very rational solution, because it will require a lot of code, but if you want such a design to be the only one, it comes to my mind. Also think that you can use regular expressions as an index of $ route, but I donโt think it can work here, since your usernames are hardly suitable for this, but I just wanted to point out the possibility.
OR
2) You can slightly change the design template and assign a different route for usernames, something along the line
$route['user/(:any)'] = "polica/ogled/$1";
This will create pretty pretty (and semantic) URLs, though, and avoid all the problems associated with avoiding other routes.