I can relate to hesitation for the window girl option and despite going to Antwerp several times, I've only done window shopping in that RLD. Other forums have said good things about the service though if it helps. I have been to a few windows in Ghent and it was a 50/50 experience. The main strip is like you feared but around the corner I had some great punts.
Not sure there's any FKK type clubs in Belgium but I do know of two PriveHuis brothel types, unfortunately I've not visited either myself but they've been on my list to visit, decent reviews on other forums for service.
External Link/Members Only - It's on the outskirts of Antwerp but not a problem if you have car.
External Link/Members Only - This one is in Ghent but it's only a short train ride from Antwerp and it's a short walk from St Pieters station.
External Link/Members Only - Also to consider this for an incall or outcall too, it covers Antwerp in the search despite it being a dutch website.
Always felt fairly safe in Antwerp, walked around the RLD very late at night but I've usually stayed within the old city. I would be a bit wary about visiting some of the suburbs for an incall however. Hope you have a great trip!
