I dont think an ip changer will help, steam is notorious for permanently banning anyone which displays suspicious activities.
The other solution would be just to buy the quake package via mail order, if you had read the link I gave you you might have noticed this statement:
Luckily there are mailorders where I can get the Quake Collection, but I have to send in a copy of my id first, to confirm that I am at least 18 years old. Why isn't such a possibility integrated in Steam? The way it is now, it might be quite pointless for some users in Germany to buy games over Steam...
Its a simple matter of contacting steam to see what they can do for you, but it may prove to be impossible for german users.
I thought that your opriginal 'wtf' from your original post displayed shock, if you knew about it already, it shouldnt have been too much of a surprise.