I have the same issue.
As we know, China and Europe use the different frequency band for wifi 5GHz. I bought the iPad in China, could I use my iPad in Europe?
For straight Wi-Fi there is no problem - you just have to change your location and time zone so your apps know where you are - and if passwords are involved, you might have change the language setup - and different countries might have different channel ranges but they overlap with the capabilities of the ipad - and there may be some legalities with the frequencies involved but I have never of an iPad police so I wouldn't worry about it - people just use there iPads where they have to.
However, iPads with cellular access are another story - their use would depend on their carrier and the availability and compatibility of the carriers in the destination country - and if service is available it could be very expensive