As I kept thinking about our squad I had come onto the thought about how we can maximize players effectiveness, the mismatch of Danilo and Sane as a LWB are examples, and how we can get around the fact that Mendy is really our only recognized LB.
I think that player's preferred foot plays a big role in where they are effective, and have outlined two rotations that would work with 3 atb if Pep persists with this:
Note: The CBs aren't mentioned because they aren't what im highlighting
Squad 1:
----------CB---------CB----------CB-------
Walker-------Dinho--------D Silva---------Mendy
---------Kevin----------Aguero--------Jesus
Squad 2:
---------CB----------CB----------CB---------
Walker-------Toure--------Gundogan----------Danilo
--------B Silva----------Sterling----------Sane
Reasons:
1) Giving Walker, Danilo and Mendy an opposite footed partner ahead of them who are B Silva Sane and Jesus respectively. In Squad 1 Kevin is in front of Walker because his crossing ability is just too good. Sane is no longer required as a wingback (this being my main reason for the formation, and Danilo of course)
2) One playmaker in the front 3, Kevin and B Silva, with opposite foots, Kevin can cross from the right (amazingly) while B Silva would cut in, offering two different sorts of playmakers. They aren't pacy, but that is not the point, they offer the same role that Eriksen at spurs has for Alli and Kane.
3) If Sane is better on the left than right (which many people including Pep may agree), than having Danilo behind might make sense, Sane can make vertical runs while Danilo can cut in.
4) Midfield pairing, while it seems odd to play D Silva this far back, next to Dinho he can perhaps be given more freedom, usually midfield duo's have a more creative option and a defensive option. Gundogan and Toure are paired because I see them as kind of hybrids, not quite as attacking as Silva or defensive as Dinho.
5) In the front 3 the aim is to have a playmaker and two goal scorers, as well as one forward who is better at crossing (Kevin and Sane) to lessen the predictability of crossing only coming from fullbacks.
6) This can be easily seen as 3-5-2 with Kevin and B Silva dropping next to D Silva and Gundogan respectively.
7) Always one Silva on the pitch, we should never be Silva-less.
Possible Negatives:
1) Questionable midfield duo-pairing. I think D Silva can work in this role, he still has license to attack but is more used for controlling the tempo of the game. Toure possibly doesn't have the legs to do it. It might be that Gundogan and D Silva would be perfect together as well.
2) Why not just use 4-3-3? In fairness the 3-4-3 is very similar to 4-3-3 if you just push up the central CB and drop the fullbacks slightly, but mainly because I think B Silva isn't a pure RW and better more interior and in Sterling I see someone who has excelled in a central attacking role, who has maybe been stifled being stuck out wide. His ability to carry the ball and run at CBs has impressed me.