I don't think they need another star in their line up ...
you are wrong if you think Derrick Rose is still a star.
he is no star anymore, if he'll ever play with the Lakers, he'll be in the 2nd unit, and my definition of a star belongs to the starter of a team.
He is still deadly in his part. He plays better offense so for me he is still a star he might not be suited to be teamed up with James. Rose played well with the ball in his hand and not by just receiving it and shoot which the Lakers doesn't need. Lakers need a streaky shooter to open up the lanes of Davis and the other bigmen to operate.
D Rose stats is picking up now, he has a great performance with the Pistons with an average of 18 points PPG already.
https://www.basketball-reference.com/players/r/rosede01.html
however, it's just sad to see that Pistons are not struggling but they'll eventually get the playoff spot even in the last spot when the full roster is healthy.