I would regard Thiago is somewhat a cross between Ronaldino and Xavi, Xavi is basically a Scholes in Barca jersey, Thiago share some of their qualities but he also has tendency to take more risk and dribbles. Scholes is the the main orchestrator in our midfield for so many years, he was basically faultless in everything except his trademark tackling. Carrick, on the other hand, was more a good ball interceptor, with good anticipation, good passer of ball and bring good positioning in our midfield. This season he has add more authority in our midfield which has made him such a great player for us. I don't see either Scholes or Carrick being good comparison with young Thiago, who is a risk taker and "likes" to dribble alot. Scholes and Carrick would cut this down in the match (not saying they can't dribble, Scholes has one of the best skills/technique in the game, but he would leave this one to Giggs and Ronaldo as it works better under our system) as they are more concerned on playing for the team in their particular role.
But I agree with everything else you've said. Just that he is from Barca academy and the fact that Guardiola will know how to use him better, makes me wonder that he may blossom more playing for Barca and Bayern in long term.