I like the idea of a title winner being in the squad for the sake of the squads mentality but think it is just a romantic notion and not actually that beneficial.
It takes most players signed 12 months to understand Poch's tactics/philosophy and by that point someone like Mascherano would have cost £6,760,000 in wages, having been our highest paid player and dwarwing the top earners of £80,000 if we matched the £130,000 he is on at Barca.
That may upset squad more than bringing it together, it may not of course. But there is a lot more to consider than just 'He's a winner'.