As others have said, allow players to select how many levels down from the current level sync they want to be on any given planet.
Planet syncs you to 34? Allow players to select up to (some arbitrary number) 8 levels down from 34, and the game will reduce your stats to that level. Players would also get more experience from quests and mobs if they complete them at nerfed levels.
I would love the opportunity to play the class stories and have the end bosses give me a significant challenge, like the vibe from 1.0.