Subboards to the multiplayer section worked perfectly fine for years and generated good interest without cluttering the rest of the forums. Ruling them out just because someone decided to reinvent the wheel is just silly and a laughable starting point if you're actually being serious (in reality you have 0 power to do anything about it so who cares). As with every change implemented recently, there is apparently never any onus on the changers to justify or present the positives of the change, and only ever the demand that we explain the obvious, meanwhile population and interaction drops off.
I guess you could recreate it by linking from the multiplayer section to the groups in an obvious Tournament This Way manner, but really that's just making the same thing really. I mean in the BL section there are individual sections for each map and class, I don't see how a few boards for running tournaments is a hassle.