Imho Bernard moves to 10 and Walcott comes in. Walcott will prob give a bit more on defensive duty too. Sigurdsson then either takes up the Gomes role as a bit deeper CM or drops to the bench if Gomes finds (real) form. I have a funny feeling that Silva will pick Morgs over Gana. If the rumours are true and we play 3 CBs then that team probably becomes:
Tosun/Walcott
Richarlison Bernard
Digne Gomes/Sig Gueye/Morgs Coleman
Zouma Mina Keane/Holgate
Pickford
Where basically the front 3 could be any combination seeing Richarlison and Walcott could play as the main forward, so Tosun drops to the bench. This also depends if Bernard is the player we hope he is and can hack it in the PL.