If we're are attacking, I don't think there are better full backs to have than Amavi and Yedlin in this division. The pace of the two of them would also be bloody frightening on the break.
The jury is out on them in terms of defense though. Maybe with Jedinak in there he might drop back to protect Elphick and Chester when these two are bombing forward? Add to this that Grealish and Ayew will not necessarily stick out wide as they tend to cut inside with the ball more often then not. We'd end up looking like this on the break
-----------------Gestede-------------------
----Grealish---McCormack----Ayew---
Amavi----------Tshibola--------Yedlin---
------------------Jedinak------------------
-----------Chester---Elphick-------------
-------------------Gollini--------------------