Implicit Aliases for the Subpages of an Alias

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I use the internationalization module for a new project. But for one page and it's subpages I want to handle the translation manualy coded in the pagetype. It will be thousands of subpages, so I want to avoid actually creating an alias for each of them.

For example, if there is a page with an URL like this:
domain.com/en/section-to-be-aliased/a-sub-page


... it should also be reachable via
domain.com/de/section-to-be-aliased/a-sub-page


... while there is only an alias for the superior page, called "section-to-be-aliased" here.

What would you suggest to be the cleanest way to do that, keeping all caching-functionality alife?

My first approache would be to inherit the Concrete5_Library_Request class and overwrite the function getRequestedPage().
But I'm wondering if there is a simpler solution. Also i recognized, that sitemap the alias shows the number of subpages of it's original ... which suggests that they are already accessable via the alias? Well I tried the corresponding URLs and they didn't work.

Thanks,
Johannes