LL deal is very complicated one, The only missing part to complete the deal is agreeing on option to buy instead of obligation.
I think the main reason why Aulas is insisting on obligation, is to make sure that if LL success with us, Marotta should pay exactly what agreed on, not to troll and don't take the option fee (8m) and push with the player for even less fee (~5m).
Just like what he did with Aquilani. He loaned him with option to buy for 15m, but eventually he didn't take that option and negotiated for 8m.
Unfortunately, I don't see Marotta agreeing on obligation with more than 6m.
So I hope that Aulas is clever enough to know that LL will be a great opportunity for any team to buy in the summer, since he will be in the last year of contract, and agrees to our current offer.