I want to see more of this.
Not ideal but there's a lot of good going on here. It won't work all the time but I actually think this is the CM position that is better suited to Santi's abilities. He doesn't have to track as much space as the holder, and he has less opposition pressure to cope with. I like using his passing range and quick decision-making to start attacks. He's not soft defensively either, he's weak physically but puts in a shift and can win some tackles.
Being solid defensively is a concern, but at the same time the way Wenger's Arsenal win games is by getting the ball to our danger men high up the pitch and working rapid combinations. I'd like to test it out one more time in a game that's high-pressure but irrelevant at the same time.