Make old champs rare drops
For the most part people don't want to pull old champs. Especially when we are talking 6* champs. It seems to be a reason why a lot of people quit actually. Save up for 6* and again get an old outdated champ for the 5th time in a row? "Screw this game, I'm out."
So what if the algorithm was designed so that old champs are a Kabam confirmed rare pull? That would change up the stigma big time. It would give them trophy champ status so that to a lot of newer players who happened to pull a Jugs wouldn't be so devastated. Plus, and I know Kabam has done a decent job of this so far, keep beefing up their synergies to make them desirable. Make old school champs have great synergy abilities the new champs can't do by themselves.