I've never been a fan of Willian and don't want us going down the route of signing average old men, but I was watching him the other day and if we can't sign a proper winger this year then maybe a 2+1yr style contract might make sense?
First, we need depth. Martinelli is probably out till 2021 which leaves us with Saka, Nelson and Pepe and maybe Auba if Laca sticks around, and two (potentially three depending on Saka) could be off to ACON if that happens. We've already got 3 really promising young players so if you want to avoid killing them someone of the profile of Willian makes sense.
Second, he keeps and carries the ball better and more consistently than any of our wide players by a huge margin, so he will be adding something. In a window where we have no money, committing 10-15m on wages over the next 2-3 years isn't that big a deal.