If you look at the minutes Wilson played last season, by comparison with previous years, you’ll see that his return is quite consistent, and 10 goals and 7 assists in the League last year was more than either Doku or Savinho could manage. He also has 17 goals in 69 international matches.
Wilson also has other attributes that we currently lack, for example he is good on set pieces (free-kicks, corners) and he can cut in and hit a cross-field ball from the right wing to the left; we currently take 3 passes to get to Doku, by which time the defence is back and it’s walking pace football again.
Wilson’s age stands against him, true, but a bit more experience in the final third wouldn’t actually go amiss, and on a free he would allow even more money to be invested in the midfield. I’m not bothered if Savinho stays, but if he does go, then I could see the merits in signing someone like Wilson, a consistent back up, over someone who struggles with the demands of the League.