I love CC, and can't wait to queue up with my friends. But, I think there needs to be a thing done first, to ensure that 5-stacks aren't the most abusive/oppressive thing ever. This is how Heroes of the Storm (a MOBA from Blizzard) does it:

First, everyone has a hidden MMR (match-making rating) associated with their account. This is technically separate from Rank, as there are de-rank protections in the seasonal rank.

Second, when forming a match, keeping MMRs close is the priority.

Third, when parties are forming, when there is a significant MMR difference within the party, the lowest MMR in the party is disregarded for the purposes of MMR matching. So if someone who has a massive MMR is partying up with newbies or smurf accounts that have tanked their MMR, it won't result in them getting put in middling MMR brackets. This also applies to 4- and 5-man parties, regardless of MMR difference--the lowest 1-2 MMRs in the party are simply disregarded.

This helps massively with 5-stacks trying to farm or cheese the matchmaking system, and also ensures that 5-stacks are going up against appropriate competition.