I don't mind keeping Vidal if he is serious about working hard to get a spot.
Of course we need a different approach in defense to cover his side, but this is the least problem of all, IMHO.
If we can make our system work as usual, playing high on pitch with fast and short passes, our defenders will play close to the half pitch line anyway...
What I really want from him is to be decent running, dribbling and making one-two combinations in the third quarter of the pitch, something he couldn't do until now...