IMO it's not good idea. I guess that if it's random, there could be a lot fights in groups, and it will just not work. Just think about if you have to play for your enemy... it will not work
PPL in clan are friends, they know themself well and it's nicer to play with clanmates. Anyway, do whatever you wish, but I'm not gonna take part in it. And it can do clan league even less active.