What the frick does any of this have to do with selling the best number 10 in England and David Future Captain Luiz?
Nothing, but I'm not particularly surprised that Mourinho is willing to listen to offers.
For example, if Mourinho employs his deep 4-3-3, Mata can play the wing, as he did at Valencia, but he isn't known for tracking back, nor is he a fast player who can drive at players in the counter-attack. The comparison to Sneijder is not accurate, as Sneijder can play much deeper than Mata, who is closer to a classic number 10 than a CM. If you want to build the team around Mata, it would be best to employ a 4-2-3-1, but Ramires and Mikel as a double pivot offers very little in terms of dynamic forward passing. Mikel fits the anchor man role that Makelele revolutionized, because he can hold the single pivot, and can offer simple passes forward.
Luiz is a bit of an enigma, as he is a superb ball playing CB who is a bit unpredictable with his positioning defensively. He's an alright passer from midfield, but in Mourinho's mind, moving from Xabi Alonso to David Luiz is a major step down in the passing department. Luiz could be the all action midfielder in a double pivot with a DLP partner, but I don't see anyone on Chelsea's roster who can fit the DLP, other than Romeu, who is a bit suspect in other areas.
In addition, these players can raise funds for players who fit into Mourinho's scheme perfectly. It would be a mistake to sell them without adequate replacements, but I can totally understand why there is talk of selling them.