Don't have a distinction between ranked/social. Allow people to get ranked in gametypes that are fundamentally the same as what everyone else plays. Build gametypes that are naturally short between teams with a wide skill-gap, and longer between those with a small skill gap.

Then, have tent-pole events centred around knock-out tournaments that use your playlist skill ratings as seeds. These tournaments would use slightly altered rule-sets to support spectatorship and make it more exciting and tense, and further tease out difference between teams. Everyone would be encouraged to get on at a certain time and play in (or watch) the tourney for bragging rights and prizes. Winners of online tourneys get automatic invites to in-person LAN tourneys at the end of the season.

Or, something like that.