I haven't seen a lot of Brewster but from what I have he's been a little underwhelming - as opposed to Jones and Williams who both look the part.
If we get Werner we have him, Origi and Minamino to compete with the established 3 and replace them when necessary. I'd expect to see more rotation then we've been used to because we can't just drop them into the gaps when ACON comes along and expect them to gel immediately.
To begin with, I'd expect to see the front 3 being subbed earlier than they tend to be now in order to give the others experience. Depending on how well they do, who knows where we go from there?