@Football Manager you've highlighted a way of using Willock in a double pivot and its flaws. But we very rarely play that system and certainly wouldn't play Willock in that role against strong opposition.
His best use (and what we should have done with Ramsey & Wilshere) is as an attacking 8 in a 3 man midfield. A lot of us suspect that a 433 is Arteta's long term dream, but I guess the reality is a hybrid of 4-3-3 and 4-2-3-1. In either event there is scope for someone with Willock's athleticism, ball carrying ability and goalscoring potential to be a contributor, but He does need to either get technically cleaner and defensively better (or both) to have any real chance of locking down a starting berth. At his current age, significant technical improvement is unlikely, but a more defined role would do his tactical intelligence the world of good.
The key thing to note is that Willock at Newcastle developed into a better, more assertive and cleverer player than we'd seen in his Arsenal cameos. He increasingly looked like someone who had worked out when to do things - ie reading the play. His athletic profile make him the kind of prospect you think long and hard before parting with, because while not quite at Ramsey's technical level (and certainly not at that of WIlshere or the aforementioned genius Cazorla), he can cover ground more effectively than all 3 combined, and is an exceptionally strong runner with the ball. He's also bigger and better in the air than all 3.
Of course a midfield composed solely of players like Willock is a chaotic version of Ardiles football, and can't work at a big club, but as a part of a squad, he could be very useful, particularly as his assets differ so much to the others at our disposal.
The point you tend to miss, being a purist, is that the best squads are a blend. Ray Parlour technically was miles behind most of the midfielders we've had in the last decade, but his stamina, determination, commitment and his providing different attributes to his peers made him a key squad member in the best Arsenal team in Living memory, with a trophy haul far more skilled players could only dream of. Not saying WIllock will ever have that impact, but then no-one would have predicted Parlour's career at the same age.
In a squad where no midfielders ever score and only 2 can run, and only 1 can beat a man, a young home-grown player who can do all 3 is worth persevering with. If AMN carried the same goal threat, we'd be looking at 40m offers rather than 15m ones.
Don't really disagree with anything here but the thing this post misses is that Willock as a squad player is just a poor use of value. Instead of a valuable £25-30m in the bank to spend on much more needed reinforcements to a squad desperately in need of reinforcements, we keep him around and watch yet another asset depreciate, just like AMN last season, who you assured me wouldn't lose value (and does anyone really think we'll get £20m for him now? I'd be happy with £10m).
No one likes seeing academy products sold (can honestly say the day I read Gnabry was going to be sold was probably the most discouraging day for me as an Arsenal fan in recent history, bar the day of the Em*ry hire), but you have to be realistic and know with which academy products it's time to cash in and get value. Willock, as someone that's extremely unlikely to be an important factor for a Champions League club in England in his future, is one of those cases, just as AMN was last summer.