But while rules are good, sticking to them no matter what is not.

Luiz ticks pretty much every box. He is a proven good PL player. We need a central midfielder. His style suits Moyes. He has a decent scoring record from PL (total 15 goals in his last two seasons) as well as creating goals (11 assists in that same period). And price doesn't sound exuberant. He would immediately improve the team massively and could conceivably play at this level for 6-8 years.

He is probably the best player in his prime that we could hope to get. I wouldn't sign more than one player at this price and age but this is the one exception I would be willing to make.