Making this work for a 1200 to 1200 bridging implementation is pretty straighforward, and there are plenty of docs on how to do this- basically, you're only going to have one SSID running between your bridges, and then set up subinterfaces for each vlan you want to carry across. However, whether this is possible when bridging to a WET200 is a very different question. I'd be surprised if you can get this working as described.