I'm looking at the Lakers and I'm reminded of what poor chemistry is all about. Even with Lebron, a walking triple double machine, and AD, they struggle from off-season personal additions.
The C's are fortunate in that Jaylen (when healthy) is willing to let Jayson be the team face... and also receive the Lions share of the team attention. He's fine with being the second banana. But if this team adds another Alpha dog shot-taker, Jaylen is not going to be a happy camper.
IMO a known veteran PG who plays hard, has league weight, respect, and solid leadership qualities... someone who has the ability to give the game what it needs. That's the best option. (If this player has a ring...all the better.) Someone the J's need to pay attention to.
Marcus goes to the bench as a sixth man where he's best suited.