Problem is we have some skillfull players that lack certain aspects in their game making it impossible to play any decent known tactics. I.e Barkley will never manage to make a throughball, Deulofeu will never run home and have ant decent tackle. Lukaku will never press the defenders, Barry is too slow to close down etc etc.
I would try something unorthodox if I was Koeman. Play 4 at the back with Williams/Mori and Coleman and Baines beeing extremely offensive. Put Barry in the centre of an defensive mid three, only opening up space with his passes, never going to far up the pitch. Beside him we put Gana and McCarthy/Davies. They can join the attack but has to put cover on our backs when they go roaming.
Then we skip wingers as I havent seen any decent wingplay the whole year, putting Mirallas or Deulofeu together with Barkley just behind Lukaku in the middle. Barkley is given the freedom to do whatever he wants except trying through-passes. That will be Deulofeu or Mirallas task.
We need more penetration, as we all do, and Barkley alone in that position is not working as he doesn't have the vision or intelligence to play people in behind the defence - Mirallas and Deulofeu has. 4-3-2-1 may be our solution.