Hmm, I'd probably just say Random selection, as that way no-body can complain about 'blah-stuck-himself-in-with-those-hardnuts'. Sure, they can complain about some teams being immortal, but team members can be swapped before the lists are released, to keep it fair
Although that might breed suspicion and contention...mmh, let's do it!
Although that might breed suspicion and contention...mmh, let's do it!