If this is the Mercure hotel on the non-Schengen-side and its shower operation is still working like it did when I last had to pay for a shower there — going on over 10 years ago at least — then it could work for at least some arriving passengers. Don’t recall if they wanted to see an onward or arriving same day boarding pass, but I think they may have as I remember they had some kind of thing they were using to write down some information.