He’s a very useful signing in my mind. Dele and Eriksen have both spent time on the right. With the situation being uncertain with Son regarding national service signing a young LW with a nose for goal now and getting him acclimated would be smart. Son/Sess - Eriksen/Maddison - Moura/Lamela with Dele the cherry on top free to play anywhere, and maybe giving Lamela/Eriksen a chance to see if one of them could make a spot deeper as a Dembele replacement.
The thing is that at the level we want to compete it’s always better to have too much talent and not enough minutes than the other way around. Injuries happen all the time. Look at City, United, Chavs - the three winning all the trophies the past 2 decades...they don’t worry about who fits in where, they sign talent and figure it out later. They also ruin some careers along the way, but perhaps that’s just collateral damage.