Worldhopping campaign ideas

I don't know if this has been covered, but I want to do a campaign that will span the cosmere. Starting in Roshar and then eventually head to Scadrial via Shadesmar, and other places as they are released. I have some ideas about having to work against the Ghostbloods and the Sons of Honor. Getting some assistance from the 17th Shard and/or Hoid, perhaps. The problem is that I am having trouble figuring out what the over all quest should be. Should it be destroying Odium and the other "evil" shards? Should it be collecting the dawnshards to merge the shards back into Adolnasium? There was a reason why he was destroyed in the first place. And for the beginning part, I'm thinking of trying to start them off doing similar arcs as Kaladin and Shallan and/or Szeth (not as them but similar situations). Not even sure how to do the assassin arc and giving a 1st level PC an honorblade lol. I'm not even sure that's a good idea or not. And advise or ideas would be greatly appreciated.