The Dutch don't appear to be able to read mode 'S' as they always give me a squawk number or let me continue with a squawk asigned by Brussel info or Langen.
Dangerous statement. Mode-S coverage is 100% in the Netherlands.
A squawk is not just for identifying you on the controllers screen of the unit you are talking to. It's also for letting others know who controls you, or not.
In any case, you'll find that if you stay outside controlled airspace, you'll be requested to squawk 7000 in any case. Only if you transit controlled airspace, you might be asked to squawk a discrete code, but that depends on the mood of the controller.